Parmesan Crusted Au Gratin Potatoes and Onions: A Decadent Comfort Food Recipe

Au gratin potatoes are a classic comfort food, perfect for a cozy night in or a special occasion. This recipe elevates the traditional dish by adding sweet caramelized onions and a generous Parmesan crust, creating a symphony of flavors and textures that will tantalize your taste buds. The creamy, cheesy potatoes, the subtly sweet and savory onions, and the crispy, golden-brown Parmesan crust combine to form a dish that is both comforting and elegant. This recipe is surprisingly easy to make, and the results are always impressive. Get ready to impress your family and friends with this incredible side dish!

## Why This Recipe Works

Several factors contribute to the success of this Parmesan crusted au gratin potatoes and onions recipe:

* **Thinly Sliced Potatoes:** Using a mandoline or a very sharp knife to slice the potatoes thinly is crucial. This ensures even cooking and allows the creamy sauce to penetrate each layer, resulting in a tender and melt-in-your-mouth texture.
* **Caramelized Onions:** Caramelizing the onions brings out their natural sweetness and adds a depth of flavor that complements the richness of the potatoes and cheese. The slow cooking process transforms the sharp, pungent onions into a sweet and savory delight.
* **Creamy Sauce:** The sauce is made with a combination of heavy cream, milk, and nutmeg. This creates a rich and flavorful base that coats the potatoes evenly and ensures they remain moist and tender during baking. Nutmeg adds a subtle warmth and complexity to the sauce.
* **Parmesan Crust:** The generous layer of Parmesan cheese on top creates a crispy, golden-brown crust that adds a delightful textural contrast to the creamy potatoes and onions. The salty, nutty flavor of the Parmesan cheese enhances the overall taste of the dish.
* **Even Baking:** Baking the au gratin potatoes at a moderate temperature for a longer period ensures that the potatoes are cooked through evenly and the sauce is properly thickened.

## Ingredients

* 2.5 lbs Yukon Gold potatoes, peeled and thinly sliced (about 1/8 inch thick)
* 2 large yellow onions, thinly sliced
* 4 tablespoons unsalted butter, divided
* 2 cloves garlic, minced
* 1 1/2 cups heavy cream
* 1 1/2 cups whole milk
* 1/2 teaspoon ground nutmeg
* Salt and freshly ground black pepper to taste
* 1 1/2 cups grated Parmesan cheese, divided
* 2 tablespoons chopped fresh parsley, for garnish (optional)

## Equipment

* Mandoline or sharp knife
* Large skillet
* 9×13 inch baking dish
* Mixing bowl
* Whisk

## Instructions

### Step 1: Prepare the Onions

1. Melt 2 tablespoons of butter in a large skillet over medium heat.
2. Add the sliced onions and cook, stirring occasionally, until they are softened and caramelized, about 20-25 minutes. Reduce the heat to low if the onions start to brown too quickly. The goal is to slowly cook them until they are sweet and golden brown.
3. Add the minced garlic to the skillet during the last minute of cooking. Stir until fragrant, being careful not to burn the garlic. Remove from heat and set aside.

### Step 2: Prepare the Potatoes

1. Preheat oven to 375°F (190°C).
2. While the onions are caramelizing, peel and thinly slice the potatoes using a mandoline or a very sharp knife. Ensure the slices are about 1/8 inch thick for even cooking. Place the sliced potatoes in a large bowl of cold water to prevent them from browning. Drain and pat dry before using.

### Step 3: Make the Cream Sauce

1. In a medium saucepan, melt the remaining 2 tablespoons of butter over medium heat.
2. Add the heavy cream, milk, and nutmeg to the saucepan. Season with salt and pepper to taste. Whisk to combine.
3. Bring the mixture to a simmer, stirring occasionally, until it thickens slightly, about 5-7 minutes. Do not boil.
4. Remove from heat and stir in 1/2 cup of the grated Parmesan cheese. The cheese will melt into the sauce, adding richness and flavor.

### Step 4: Assemble the Au Gratin

1. Grease a 9×13 inch baking dish with butter.
2. Arrange a layer of potato slices in the bottom of the dish, overlapping them slightly.
3. Spread a layer of caramelized onions over the potatoes.
4. Pour about one-third of the cream sauce over the potatoes and onions, ensuring they are evenly coated.
5. Repeat the layers of potatoes, onions, and cream sauce two more times, ending with a layer of cream sauce on top. Be sure to distribute the onions evenly throughout the layers.
6. Sprinkle the remaining 1 cup of grated Parmesan cheese evenly over the top of the au gratin.

### Step 5: Bake the Au Gratin

1. Cover the baking dish with aluminum foil.
2. Bake in the preheated oven for 45 minutes.
3. Remove the foil and continue baking for another 20-25 minutes, or until the potatoes are tender and the Parmesan crust is golden brown and bubbly. A knife inserted into the center of the potatoes should meet little to no resistance.
4. If the top is browning too quickly, you can loosely tent the dish with foil during the last 10 minutes of baking.

### Step 6: Rest and Serve

1. Remove the au gratin from the oven and let it rest for 10-15 minutes before serving. This allows the sauce to thicken slightly and the flavors to meld together.
2. Garnish with chopped fresh parsley, if desired.
3. Serve hot and enjoy!

## Tips for Success

* **Use a Mandoline:** A mandoline is the best way to achieve consistently thin potato slices. If you don’t have a mandoline, use a very sharp knife and take your time to slice the potatoes as thinly as possible.
* **Don’t Skip the Soaking:** Soaking the potato slices in cold water helps to remove excess starch, which prevents them from sticking together and ensures a creamier texture.
* **Caramelize the Onions Properly:** Don’t rush the caramelization process. Low and slow cooking is the key to bringing out the natural sweetness of the onions. Stir frequently to prevent burning.
* **Adjust Seasoning:** Taste the cream sauce before adding it to the potatoes and adjust the seasoning as needed. Salt and pepper are essential for bringing out the flavors of the dish.
* **Use Freshly Grated Parmesan:** Freshly grated Parmesan cheese melts more evenly and has a richer flavor than pre-shredded cheese. Avoid using the powdery “shake” cheese. The quality of the parmesan makes a big difference in the crust.
* **Let it Rest:** Allowing the au gratin to rest for a few minutes after baking is important for allowing the sauce to thicken and the flavors to meld together. This will also make it easier to slice and serve.

## Variations

* **Add Herbs:** Experiment with different herbs, such as thyme, rosemary, or sage, to add more flavor to the dish. Add them to the cream sauce or sprinkle them over the potatoes before baking.
* **Use Different Cheeses:** Try using a combination of cheeses, such as Gruyere, Swiss, or cheddar, for a different flavor profile. Blend them with the Parmesan or use them as a substitute.
* **Add Bacon or Ham:** Cooked bacon or ham can be added to the layers of potatoes and onions for a heartier dish. Chop the bacon or ham into small pieces and sprinkle them over the potatoes before adding the cream sauce.
* **Add Vegetables:** Consider adding other vegetables, such as mushrooms, bell peppers, or spinach, to the au gratin. Sauté the vegetables before adding them to the layers of potatoes and onions.
* **Make it Spicy:** Add a pinch of red pepper flakes to the cream sauce for a touch of heat.
* **Garlic Lovers Version:** Add extra minced garlic to the cream sauce for an even more garlicky flavor.
* **Sweet Potato Variation:** Substitute some or all of the Yukon Gold potatoes with sweet potatoes for a sweeter, earthier flavor.

## Serving Suggestions

Parmesan crusted au gratin potatoes and onions are a versatile side dish that pairs well with a variety of main courses. Here are a few serving suggestions:

* **Roasted Chicken or Turkey:** Au gratin potatoes are a classic accompaniment to roasted poultry.
* **Grilled Steak or Pork Chops:** The richness of the au gratin potatoes complements the savory flavors of grilled meat.
* **Baked Ham:** This is a perfect pairing for a holiday meal.
* **Vegetarian Entrees:** Serve alongside a hearty vegetarian dish, such as lentil loaf or stuffed bell peppers.
* **Holiday Dinners:** This is a showstopping side dish for Thanksgiving, Christmas, or Easter.
* **Special Occasions:** Impress your guests with this elegant and flavorful dish at your next dinner party.

## Make Ahead Instructions

You can prepare the Parmesan crusted au gratin potatoes and onions ahead of time and bake it later. Here’s how:

1. Assemble the au gratin according to the recipe instructions up to the point of baking.
2. Cover the baking dish tightly with plastic wrap and refrigerate for up to 24 hours.
3. When ready to bake, remove the plastic wrap and let the au gratin sit at room temperature for 30 minutes.
4. Bake according to the recipe instructions, adding an extra 10-15 minutes to the baking time if necessary.

## Storage Instructions

* **Refrigerating:** Leftover au gratin potatoes can be stored in an airtight container in the refrigerator for up to 3-4 days.
* **Reheating:** Reheat the au gratin in a preheated oven at 350°F (175°C) until heated through. You can also reheat it in the microwave, but the texture may not be as good. It’s best to add a splash of cream or milk before reheating to prevent it from drying out.

## Nutritional Information (approximate per serving)

* Calories: 450-550
* Fat: 30-40g
* Saturated Fat: 20-25g
* Cholesterol: 150-200mg
* Sodium: 300-400mg
* Carbohydrates: 30-40g
* Fiber: 2-3g
* Sugar: 5-7g
* Protein: 15-20g

**Note:** Nutritional information is approximate and may vary depending on the specific ingredients used and portion sizes.

## Conclusion

This Parmesan crusted au gratin potatoes and onions recipe is a delightful twist on a classic dish. The combination of creamy potatoes, sweet caramelized onions, and a crispy Parmesan crust is simply irresistible. Whether you’re looking for a comforting side dish for a cozy night in or an elegant addition to a special occasion, this recipe is sure to impress. So, gather your ingredients, follow the instructions, and get ready to enjoy a truly decadent and delicious experience!