Preheat oven to 375°. In a large oven-proof skillet over medium heat, melt butter with olive oil. Add broccoli and season with salt and pepper. Cook until bright green and crisp tender, about 5 minutes. Stir in garlic and cook until fragrant, about 1 minute.
Pour heavy cream over broccoli then top with mozzarella, Gruyere, Parmesan and red pepper flakes. Bake until cheese is bubbly and broccoli is tender, about 10 minutes. (If your cheese won't brown, heat under the broiler, 1 minute).
Serve immediately.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2019/04/20/cheesy-baked-broccoli/