Preheat oven to 350°
Butter a 10-inch gratin baking dish.
Cook the cauliflower florets in a large pot of boiling salted water for 5 to 6 minutes until tender but still firm.
In a heavy saucepan over medium heat, melt butter and whisk in the flour. Stir to blend and cook for I minute. Gradually add the milk while constantly whisking.
Add the goat cheese and one and a half cups of shredded cheese to the mixture and whisk until it has thickened.
Pour the sauce over the cauliflower in the buttered gratin dish and top with the remaining Parmesan cheese.
Bake until the cauliflower is tender and the top bobbly and golden brown.
Let it rest for a few minutes before serving.
