Gratin de pommes de terre à l’oignon caramélisé et Gruyère is a classic French-inspired comfort dish that combines thinly sliced potatoes, slow-cooked sweet onions, and nutty, melted Gruyère cheese baked together in a creamy sauce. This dish is elegant enough for a dinner party yet hearty and familiar enough for a cozy family meal. Its appeal lies in the balance of flavors: the natural starchiness of potatoes, the deep sweetness of caramelized onions, and the rich umami character of Gruyère.

What Is Gratin de Pommes de Terre?

Gratin de pommes de terre is a baked potato dish traditionally made with sliced potatoes, cream, and cheese, cooked until tender with a golden, bubbling top. Unlike mashed potatoes or roasted potatoes, a gratin relies on slow baking and layering to develop a creamy interior and crisp surface.

When caramelized onions and Gruyère are added, the dish becomes more complex and aromatic. The onions bring sweetness and depth, while Gruyère—a firm Swiss cheese—adds a slightly salty, nutty flavor that melts beautifully.

Why You’ll Love This Recipe

Rich and comforting: Creamy potatoes and melted cheese make this dish deeply satisfying.
Elegant yet simple: Perfect for both casual meals and special occasions.
Make-ahead friendly: Ideal for entertaining or holiday meals.

Versatile: Works as a main dish or a side.
Authentic flavor: Inspired by classic French cooking techniques.

Ingredients Overview

Choosing high-quality ingredients is essential for the best gratin de pommes de terre.

Main Ingredients

Potatoes: Yukon Gold or russet potatoes are ideal due to their starch content and creamy texture.
Onions: Yellow onions work best for caramelization, offering balanced sweetness.
Gruyère cheese: Freshly grated Gruyère provides superior melting and flavor.

Heavy cream: Creates a rich, silky sauce.
Milk: Lightens the cream without sacrificing texture.
Butter: Adds richness and prevents sticking.

Garlic: Enhances depth and aroma.
Salt and pepper: Essential for seasoning each layer.
Nutmeg (optional): A classic addition to French gratins.

The Role of Caramelized Onions

Caramelized onions are the heart of this recipe. Slowly cooking onions over low heat transforms their natural sugars into a deep, golden sweetness. This process can take 30–40 minutes but is crucial for achieving a balanced flavor.

Unlike sautéed onions, caramelized onions are soft, jammy, and intensely flavorful. They contrast beautifully with the creamy potatoes and savory Gruyère.

Choosing the Right Cheese: Why Gruyère?

Gruyère is a traditional choice for gratins because:

It melts smoothly without becoming greasy.
It has a nutty, slightly sweet flavor.
It browns well, creating a golden crust.

You may substitute Emmental, Comté, or a mix of Gruyère and Parmesan, but authentic flavor is best achieved with Gruyère.

Equipment You’ll Need

Mandoline or sharp knife
Large skillet

Medium saucepan
Whisk
Baking dish (9×13 inches recommended)

Aluminum foil

Step-by-Step Recipe Instructions

Ingredients (Serves 6–8)

2.5 lbs (1.2 kg) potatoes, peeled and thinly sliced
2 large yellow onions, thinly sliced

2 cups (200 g) Gruyère cheese, grated
1 ½ cups heavy cream
1 cup whole milk

2 tbsp butter
2 cloves garlic, minced
Salt and freshly ground black pepper, to taste

¼ tsp ground nutmeg (optional)

Step 1: Caramelize the Onions

In a large skillet, melt butter over low heat. Add sliced onions and a pinch of salt. Cook slowly, stirring occasionally, for 30–40 minutes until golden brown and sweet. Set aside.

Step 2: Prepare the Cream Mixture

In a saucepan, combine cream, milk, garlic, nutmeg, salt, and pepper. Warm gently over medium-low heat without boiling.

Step 3: Assemble the Gratin

Butter the baking dish. Layer half of the potatoes evenly. Season lightly, then add half of the caramelized onions and a third of the cheese. Repeat layers and finish with remaining cheese.

Step 4: Add the Cream

Pour the warm cream mixture evenly over the potatoes, pressing gently to ensure coverage.

Step 5: Bake

Cover with foil and bake at 375°F (190°C) for 45 minutes. Remove foil and bake an additional 25–30 minutes until golden and bubbly.

Step 6: Rest and Serve

Allow the gratin to rest for 10–15 minutes before serving.

Expert Tips for the Perfect Potato Gratin

Slice potatoes evenly for uniform cooking.
Do not rinse potatoes after slicing; starch helps thicken the sauce.

Season every layer for balanced flavor.
Use freshly grated cheese for best melting.

Variations and Add-Ins

Herbs: Add thyme or rosemary for aroma.

Protein: Incorporate ham or bacon for a heartier dish.
Vegetarian upgrade: Add sautéed mushrooms or leeks.
Lighter version: Use half-and-half instead of heavy cream.

Serving Suggestions

Gratin de pommes de terre pairs well with:

Roast chicken or beef
Grilled lamb

Green salad with vinaigrette
Steamed vegetables

Storage and Reheating

Refrigeration: Store leftovers in an airtight container for up to 4 days.

Freezing: Freeze for up to 2 months, though texture may slightly change.
Reheating: Warm in the oven at 325°F (165°C) until heated through.

Nutritional Information (Approximate per Serving)

Calories: 380

Protein: 14 g
Fat: 26 g
Carbohydrates: 26 g

Frequently Asked Questions

Can I make this gratin ahead of time?

Yes. Assemble and refrigerate up to 24 hours in advance. Bake before serving.

Can I use other cheeses?

Yes, but Gruyère provides the most authentic flavor and texture.

Why is my gratin watery?

This usually occurs if potatoes are rinsed or if cream mixture is too thin.

Final Thoughts

Gratin de pommes de terre à l’oignon caramélisé et Gruyère is a timeless dish that showcases the elegance of simple ingredients prepared with care. Its creamy texture, rich flavor, and golden crust make it a standout addition to any table. Whether you are cooking for guests or enjoying a comforting meal at home, this gratin delivers satisfaction in every bite.

By following this detailed guide, you can confidently prepare a restaurant-quality potato gratin that reflects the best of French-inspired home cooking.

Gratin de Pommes de Terre with Caramelized Onion and Gruyère

Author: WAFA LI

Print Recipe

Ingredients

• 2 tbsp butter or olive oil
• 2 large yellow onions, thinly sliced
• 1 tbsp balsamic vinegar (optional, deepens sweetness)
• 1½ lbs (700g) Yukon Gold or Russet potatoes, peeled & thinly sliced (⅛” thick)
• 1½ cups (360ml) heavy cream (or half-and-half for lighter version)
• 1 garlic clove, minced
• 1½ cups (150g) shredded Gruyère cheese
• ¼ tsp freshly grated nutmeg
• Salt & black pepper to taste
• Pinch of thyme leaves (optional)

Instructions

Caramelize onions: Melt 1 tbsp butter in a skillet over medium-low. Add onions; cook 25–30 min, stirring occasionally, until deep golden. Add balsamic vinegar (if using); cook 1 more min. Set aside.
Preheat oven to 375°F (190°C). Butter a 9×9″ or 2-qt baking dish.

In a bowl, whisk cream, garlic, nutmeg, salt, and pepper.
Layer:
– Bottom: ⅓ potatoes (slightly overlapping)
– ½ caramelized onions
– ½ Gruyère
– Drizzle with ⅓ cream mixture
Repeat layers. Top with remaining potatoes, remaining cream, and remaining cheese.
Cover with foil; bake 45 min. Uncover; bake 25–30 min more until top is golden and potatoes pierce easily with a knife.

Rest 15 min before serving—this sets the creamy layers beautifully.