Set the pressure cooker to sauté mode and melt the butter with olive oil.
Add sliced onions and sauté until caramelized, about 15 minutes.
Add beef broth, white wine, Worcestershire sauce, and season with salt and pepper.
Seal the pressure cooker and cook on high pressure for 10 minutes. Allow a natural release for 5 minutes.
While the soup cooks, toast the French bread and sprinkle with Gruyère cheese.
Ladle the soup into bowls, top with cheesy toast, and serve hot.