Zucchini Gratin

1. Preheat Oven and Prepare Dish

Preheat your oven to 425 degrees and butter an 8 × 10-inch oval gratin dish.

2. Cook Onion

In a medium pot or Dutch oven, melt 3 tablespoons of butter over medium-low heat. Add the sliced onion and cook it slowly for about 10 to 15 minutes until it's tender but not browned.

3. Cook Zucchini

Add the zucchini to the pot, along with 2 teaspoons of kosher salt. Cover the pot and cook for 15 minutes, then uncover and cook for an additional 10 minutes, stirring occasionally.

4. Make Cream Sauce

Sprinkle the flour over the zucchini-onion mixture and stir well. Raise the heat to medium-high and slowly add the half-and-half, stirring constantly. Allow each addition of half-and-half to come to a boil before adding more.

5. Season Mixture

Remove the pot from the heat and stir in the thyme, nutmeg, 1 teaspoon of salt, and ½ teaspoon of freshly ground black pepper.

6. Prepare Gratin Dish

Spoon the mixture into the prepared gratin dish, flattening it out evenly.

7. Add Topping

In a small bowl, combine the bread crumbs and grated Gruyère cheese. Sprinkle this mixture evenly over the zucchini.

8. Add Butter and Bake

Cut the remaining 2 tablespoons of butter into small pieces and scatter them on top of the bread crumb mixture. Bake the dish in the preheated oven for about 20 minutes, until the top is browned and the gratin is bubbly.

9. Let it Sit

Allow the bake to sit for about 10 minutes before serving, letting the flavors meld and the bake set slightly.