In a large skillet over medium heat, melt butter with olive oil.
Add sliced onions, sugar, salt, and pepper. Cook, stirring occasionally, until deep golden brown and caramelized, about 25–30 minutes.
Add minced garlic and cook for another 1–2 minutes.
Make onion soup base:
Sprinkle flour over onions and stir for 1–2 minutes.
Gradually add beef broth while stirring to avoid lumps.
Add Worcestershire sauce and thyme. Simmer 5 minutes until slightly thickened.
Assemble casserole:
Transfer onion mixture to a greased baking dish.
Top with toasted bread slices, then sprinkle shredded cheese evenly over the top.
Bake:
Bake for 20–25 minutes, or until the cheese is melted, bubbly, and lightly browned.
Serve:
Let the casserole cool slightly before serving. Scoop into bowls and enjoy the rich, savory flavors!
Tips:
For extra flavor, add a splash of white wine or sherry to the onions while caramelizing.
This casserole is great as a main dish with a side salad or as a hearty side for roasted meats.
Leftovers reheat well in the oven or microwave.
I can also give you a one-pot, quicker French Onion Casserole version that skips the toasting step but keeps it cheesy and delicious. Want me to do that?
