Into a skillet, melt the butter and sauté the onion, add the wheat flour, and mix it all for 1 minute. Add the milk gradually and keep stirring it. Mix it all for another minute.
Add the nutmeg and the salt, mix it all together very well until it thickens.
Add the precooked cassava into a glass baking dish, cover it with the white sauce, add the mozzarella cheese, and top it with the fried bacon.
Bake in a preheated oven at 180°C (356°F) for 15 minutes.
Help yourself.