Savory Vegetable Gratin with Nutmeg

By AislePrompt Editorial · Published 2026-04-04 · Updated 2026-04-04

How this recipe was made — this recipe was drafted by AislePrompt's AI-assisted pipeline from technique templates and USDA-sourced nutrition data, and published by AislePrompt Editorial — see how AislePrompt recipes are developed and reviewed.

A layered gratin featuring seasonal vegetables slowly baked to golden perfection, embodying the thoughtful care required for a truly serious side dish. This French-inspired vegetarian recipe, ready in about 80 minutes, pairs potatoes, zucchini, red onion for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 320 calories and feeds 6, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Prep: 30 min Cook: 50 min Serves 6 French cuisine 320 cal/serving

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Ingredients

2 medium, thinly sliced potatoes
1 medium, thinly sliced zucchini
1/2 medium, thinly sliced red onion
3 tbsp, chopped fresh thyme
2 tbsp all-purpose flour
1 cup whole milk
3 tbsp unsalted butter
1 cup grated Gruyère cheese
1/2 cup grated Parmesan cheese
1/4 tsp fresh nutmeg
1/2 tsp sea salt

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Instructions

Step 1: Preheat oven to 375°F. In a saucepan, melt 3 tbsp unsalted butter over medium heat, then whisk in 2 tbsp all-purpose flour to form a roux, cooking for 1 minute until golden.
Step 2: Gradually whisk in 1 cup whole milk while simmering for 4 minutes until thickened, then stir in 3 tbsp chopped fresh thyme, 1/4 tsp fresh nutmeg, and 1/2 tsp sea salt.
Step 3: In a 9x13-inch baking dish, layer 1/3 of the 2 sliced potatoes, 1/3 of the sliced zucchini, and 1/3 of the sliced red onion, then pour 1/3 of the cheese sauce over the top. Repeat layers twice, ending with a final layer of cheese sauce.
Step 4: Sprinkle 1 cup grated Gruyère and 1/2 cup grated Parmesan evenly over the surface, then bake uncovered for 50 minutes until bubbling and golden brown around the edges.