Finely chopped onions.
Melt butter in a large casserole dish. Add onions and cook on low heat until onions became translucent. Monitor cooking process.
Add flour, mix and brown for 2 minutes. Pour chicken stock and white wine. Peel and press garlic. Add pepper. Cover and leave to cook for 20 minutes. Reserve.
Preheat your oven to 200°C (390°F) 20 minutes before serving. Toast bread slices. Add bread at the bottom of single oven dishes, like this little red one I used. Pour some onion soup on top of bread slices. Add grated cheese on top and bake for 10 minutes until cheese melt.
Serve immediately.