Peel the onion and chop finely. Cut the rolls into approx. 1.5 cm thick slices.
Grease a flat baking dish with a little butter, layer the bread rolls like a roof tile and drizzle with the wine. Put the cheese slices between the bread rolls. If you like it strong, you may like a more flavorful cheese, e.g., not too old mountain cheese.
Melt the remaining butter and sauté the onions until translucent.
Whisk the eggs and cream, season with pepper, nutmeg and about half a teaspoon of salt and pour over the casserole. Spread the steamed onions over the top.
Close the form with a lid and bake in a preheated oven at 200 ° C for about 30 minutes. Then bake without the lid for another 10-15 minutes, until the onions and bread rolls are lightly brown.
Garnish with chopped chives before serving.
A fresh leaf salad tastes good with it, e.g., Field salad with a fruity cranberry dressing.