Cut or break the cauliflower into smaller pieces.
Slice the chicken breast about 1/2" - 3/4" thick.
Put the cauliflower pieces in boiling water and cook it for about 5 minutes (or until it's softened, but still not cooked completely)
Sauté the chicken breast slices in the 1 tbsp butter. About 3-4 minutes per side.
While the cauliflowers and the chicken breasts slices are getting ready, make the bechamel sauce.
Melt the butter in a saucepan, add the salt, pepper and the nutmeg.
Add the flour and whisk it in the butter.
Pour the milk on them, whisk it until you get a smooth sauce.
Cook it for about 5 minutes, or until it thickens.
Put the sautéed chicken breast slices to a casserole.
Layer the cauliflower pieces on the chicken.
Pour the bechamel sauce on top.
Add the grated cheese.
Bake it on 350-360° for 10-15 minutes or until the cheese melts and get a nice golden color.