2 large onions, sliced into thin rings
1/4 cup butter or margarine
6 hard-boiled eggs, cut into slices
Salt and black pepper to taste
For the cheese sauce
2 tablespoons butter or margarine
2 tablespoons all-purpose flour
1 2/3 cups warmed heavy cream
1 tablespoon prepared mustard
2 tablespoons grated cheddar cheese or Parmesan cheese
1 egg yolk
2 tablespoons milk
2 large onions, sliced into thin rings
1/4 cup butter or margarine
6 hard-boiled eggs, cut into slices
Salt and black pepper to taste
For the cheese sauce
2 tablespoons butter or margarine
2 tablespoons all-purpose flour
1 2/3 cups warmed heavy cream
1 tablespoon prepared mustard
2 tablespoons grated cheddar cheese or Parmesan cheese
1 egg yolk
2 tablespoons milk
Fry the onion in butter or margarine until softened, about 5-7 minutes, stirring constantly over medium heat without browning
Prepare the cheese sauce: melt the butter and add the flour, stirring well
Add the warmed heavy cream, stirring well
Add the mustard and cheese, and cook for an additional 2-3 minutes or until thickened
Beat the egg yolk with milk until smooth
Remove the pan from heat and add this mixture to the saucepan, stirring until smooth
Grease a glass baking dish refractory and arrange in layers alternating onion and egg slices
Sprinkle with salt and black pepper and pour the cheese sauce on top
Bake at 220°C (400°F) until golden brown and starting to bubble
Serve as a snack, accompanying bread or toast, for 6 servings.