Peel and halve the onions and cut into fine strips. Steam these in hot clarified butter with a little water and the lid closed for 15 minutes. Remove from heat and season.
Dissolve the yeast in a little milk. Knead the flour, salt, sugar, the yeast dissolved in the milk, the milk and the oil to form a smooth dough. Let rise in a warm place for about 40 minutes until it has doubled in size.
Dust the dough with flour and knead again.
Preheat the oven to 200 ° top / bottom heat.
Roll out the dough thinly on a floured work surface and place on a greased baking sheet. Cover with the steamed onions and bake for 20 minutes.
After 10 minutes, sprinkle the cheese on the thin slices and finish baking.