Zucchini gratin

Ingredients:

• 900 g (4 pcs.) zucchini, halved and sliced
• 2 teaspoons coarse salt
• 1 teaspoon freshly ground black pepper
• 1/4 tsp ground nutmeg
• 2 tbsp. premium wheat flour
• 1 cup of hot milk
• 3/4 cup fresh bread crumbs
• 3/4 tbsp. grated gruyere cheese
• 450 g (3 large) onions, cut into half rings
• 6 tbsp (80 g) unsalted butter, plus extra for soaking

Preparation:

1. Preheat oven to 205°C.
   
   In a very large saucepan (12 inches in diameter), melt the butter and sauté the onion over low heat for 20 minutes, or until softened but not browned. Add the zucchini and simmer, covered, for 10 minutes, or until softened. Season with salt, pepper, and nutmeg and cook, uncovered, for another 5 minutes. Stir in the flour. Add the hot milk and simmer over low heat for a few minutes until a sauce forms. Pour the mixture into an 8x10 inch baking dish.
   
   Mix breadcrumbs and Gruyère cheese and sprinkle over the casserole. Spread small pieces of butter (about 1 tablespoon total) over the surface of the gratin and bake for 20 minutes, or until the crust is golden brown and the sauce is bubbling.