French Onion Gnocchi Gratin with Melted Gruyère Tips, FAQ & printable recipe

Tips for success

To achieve the best flavor, do not be afraid to let the onions cook longer than you think. The difference between golden onions and truly caramelized, jammy onions is often just an extra ten minutes of low, slow heat. If the onions start to stick too much, add a tablespoon of water or a tiny splash of broth to deglaze the skillet, which helps lift the fond—the flavorful browned bits—back into the mix, enhancing the overall depth of the dish.

When adding the broth and cream, start with a slightly lower heat to allow the gnocchi to warm through without the sauce reducing too rapidly. If the sauce seems too thick before adding the cheese, add a small splash of additional broth to reach your desired consistency.

Remember that the cheese will add a layer of fat and richness, so keeping the sauce slightly thinner before broiling is often better, as it will thicken further while in the oven.

Variations

• Mushroom Onion Gnocchi: Add 200 grams of sliced cremini mushrooms to the skillet along with the onions. Sauté until the mushrooms are browned and their liquid has evaporated, then continue with the recipe as written for a deeper, earthier flavor profile.
• Spinach Gnocchi Gratin: Stir in 2 cups of fresh baby spinach during the final minute of simmering the gnocchi. The spinach will wilt quickly into the sauce, adding a touch of color and a fresh, vibrant element to the rich gratin.

Storage and make-ahead

Fridge

Store in an airtight container for up to 3 days.

Reheat

Reheat in a preheated oven at 350°F (175°C) until warmed through, or on the stovetop over low heat, adding a splash of broth if needed to loosen the sauce.

If you have leftovers, allow the skillet to cool completely at room temperature for no more than two hours. Once cooled, transfer the gnocchi to an airtight container. It will keep well in the refrigerator for up to three days. When ready to eat, reheat it gently on the stovetop or in the oven, adding a tablespoon of broth or water if the sauce has thickened too much during storage, to restore its original creamy texture.

You can caramelize the onions up to two days in advance and store them in the refrigerator. When you are ready to make the full dish, simply heat the prepared onions in your skillet, then proceed with the recipe as instructed.

This shortcut significantly reduces the active cooking time on the day of serving, making it a convenient option for busy weeknights. However, it is best to prepare the gnocchi and broil the cheese fresh to ensure the best texture and quality.

Serving ideas

This gratin is best served directly from the skillet to maintain its temperature and the integrity of the melted cheese crust. Place the skillet on a heat-proof trivet in the center of the table.

Serve with a large spoon to ensure each portion gets a generous amount of the caramelized onions and the crispy, cheesy edges. Because the dish is quite rich, it pairs beautifully with a simple, crisp green salad dressed with a light vinaigrette to balance the flavors.

For a more complete meal, consider serving the gratin with a side of crusty bread or a warm baguette, which is perfect for mopping up any remaining onion broth and sauce. The contrast between the soft gnocchi and the crunchy bread adds another layer of texture to the meal.

If you prefer, a side of roasted vegetables like asparagus or green beans also works well, providing a fresh element that complements the savory and creamy nature of the main dish.

Frequently asked questions

Recipe card

French Onion Gnocchi Gratin with Melted Gruyère

Prep 15 minCook 45 minRest 5 minTotal 1 h 5 minServes 4

Ingredients

• 600 grams sweet onions, sliced
• 50 grams butter
• 1 tbsp thyme
• 45 ml dry white wine
• 500 grams gnocchi
• 350 ml beef bone broth
• 80 ml cream
• 180 grams Gruyère cheese, shredded

Instructions

1. Place the cast-iron skillet over medium heat and melt the butter. Add the sliced sweet onions, thyme, and a pinch of salt. Cook, stirring occasionally, until the onions are deep golden brown and jammy, which should take about 20 minutes. Pour in the dry white wine to deglaze the skillet, scraping up any browned bits from the bottom, and cook until the liquid has mostly evaporated.
2. Add the gnocchi to the skillet with the caramelized onions. Pour in the beef bone broth and cream. Bring the mixture to a gentle simmer at 194°F (90°C), ensuring the gnocchi are submerged in the liquid. Cook for 3 to 5 minutes until the gnocchi are tender and the sauce has thickened slightly.
3. Evenly spread the shredded Gruyère cheese over the top of the gnocchi mixture. Place the skillet under a preheated broiler set to 446°F (230°C). Broil for 3 to 5 minutes, or until the cheese is melted, bubbling, and blistered with golden-brown spots. Remove carefully from the oven and let rest for 5 minutes before serving.

Contains: gluten, milk, sulfites

Estimated nutrition per serving

Calories

480

Protein

14.5 g

Carbohydrates

45.2 g

Fat

26.8 g

Fiber

3.5 g

Sugar

8.2 g

Sodium

750 mg

Automatic estimate from the ingredient list, not laboratory-verified.