1 head of cauliflower, broken up into florets
2 tablespoons olive oil
4 tablespoons butter, divided
1 medium onion, sliced
6 ounces (about 3 slices) prosciutto, chopped
3 cloves garlic, minced
1 cup heavy cream
1/2 cup Parmesan cheese, grated
1 cup mozzarella cheese, shredded
1 teaspoon salt, divided
1/4 teaspoon black pepper
Preheat the oven to 350 degrees Fahrenheit. Place the cauliflower in a steamer basket in a pot with about an inch of water. Sprinkle the cauliflower with 1/2 teaspoon salt. Cover, turn heat to high and once the water begins to boil and the pot begins to steam, steam cauliflower for about 5 minutes until soft. When cauliflower is finished cooking, transfer florets to a large bowl.
As the cauliflower is steaming, place the olive oil and two tablespoons of butter in a non-stick pan over medium-low heat. When the butter has melted add the onion slices and cook slowly, stirring often, for about 30 minutes until they have begun to caramelize. When finished, add them to the bowl with the cauliflower.
As the onion caramelizes, place the chopped prosciutto in another pan and fry over medium heat until crispy. Add the crispy pieces to the bowl with the cauliflower.
To the same pan you cooked the prosciutto in, add the remaining 2 tablespoons of butter and minced garlic. Saute for about one minute over medium heat then add the heavy cream, Parmesan cheese, and mozzarella cheese. Season with remaining 1/2 teaspoon of salt and black pepper. Cook for about ten minutes until the cream mixture has thickened and then add to the bowl with other ingredients.
Stir all ingredients together and transfer to a 9" x 13" casserole dish. Place in the oven for 15 minutes.