It's a simple dish:
3 onions, chopped - caramelize deeply with butter
2 cloves garlic, mince and saute shortly
1 cup milk 3% fat (220 ml)
3 tbsp flour
1/2 tsp baking powder
nutmeg, to taste (about 1/4 tsp, but depends on freshness)
salt, to taste (about 1 tsp)
optional: chopped parsley
optional: Grated cheese such as Gruyere or Emmental.
Pour into lightly oiled pan.
Bake apx 45 minutes at 180 deg C (it should be set, but don't over bake).
Let chill well, otherwise it will be liquidy. Can be made ahead.
Best reheated before eating