Peel and chop shallots and garlic. Heat a cooking pan over low medium heat. Melt 1/2 oz of butter, add shallots and garlic. Leave covered for 5 mn, moving it a few times. Add spinach. After 5 to 7 mn, add salt and pepper and set aside.
Melt 2 1/2 oz of butter in a cooking pan. Sprinkle with flour, let it get a golden color and add cold milk. Add a little salt, pepper and nutmeg. Then add cheese. Stir well and take off heat.
Separate egg whites from yolks. (The easiest way to do it is by taking the broken egg in one hand and let white fall in a bowl when keeping yolk over your fingers). Add yolks to cheese sauce. Beat egg whites until stiff.