Bring a large pot of water to boil. Add cauliflower, boil 2 minute Add sprouts, boil 4 minutes. Drain the veggies.
Melt half the butter in a sauce pan. Sprinkle in the flour and stir until it makes a paste. (your making a white sauce here, you've probably figured out.) Slowly pour in milk while stirring. Let it simmer a bit until thickened.
Now its cheese time! Add your cheeses, nutmeg, salt pepper. Add the cheeses bit by bit, stirring to make sure everything is smooth and melted.
In a casserole dish, pour enough of the cheese sauce in to cover the bottom. Add in your sprouts and cauliflower. Pour the rest of the sauce on top. Give everything a little mix so the veggies are all covered in cheesy goodness.
Top with breadcrumbs. Melt other half of butter and pour over breadcrumbs.