Method

• Melt butter on medium heat in a medium sized saucepan. Add the sliced leeks and gently cook until completely softened, about 8 to 10 minutes.
• While the leeks are cooking, place cauliflower florets in a steamer basket in a saucepan over an inch of water. Bring water to a boil, cover, and steam the cauliflower for 3 to 4 minutes. Remove strainer and cauliflower from hot pan and set aside.
• Add 2 tablespoons of flour to the leeks and butter. Stir and let cook for a minute or two. Slowly add the milk, stirring as you add it to break up any lumps. Bring to a low simmer and continue to stir as the sauce thickens.
• Once the sauce is thick enough to coat the back of a spoon, stir in 3 ounces of the shredded cheese (reserving the rest of the cheese for the topping), the thyme, nutmeg, and salt.
• Preheat the oven to 400°F.
• Spread a teaspoon of butter over the insides of a 2-quart gratin dish. Place the lightly steamed cauliflower florets in an even layer in the dish. Pour the leek and cheese sauce over the cauliflower. Top with remaining cheese. Bake for 25 minutes.
• While the gratin is baking, melt 1 tablespoon of butter in a small sauté pan on medium high heat. Add the fresh breadcrumbs and toast in the melted butter for 4 to 5 minutes, until lightly browned. Sprinkle with ¼ teaspoon of salt, and a sprinkling of pepper. Remove from heat.
• After the gratin has baked for 25 minutes, remove it from the oven. Sprinkle toasted breadcrumbs over the top and return to the oven. Bake for 5 more minutes.