Add the butter and olive oil to a large skillet and heat over medium-low heat. Once the butter has melted, add the onion slices and cook for about 5 minutes until the onion starts to caramelize.

Add the cauliflower florets, cremini mushrooms, Italian seasoning, salt, pepper, and vegetable broth to the skillet and cook for about 10 minutes until the mushrooms and cauliflower brown.

Add the garlic and cook for another 30 seconds until aromatic. Taste for seasoning and adjust with salt and pepper as needed.

Garnish with red pepper flakes and parsley.