Preheat your oven to 350°F (175°C).
Tear the croissants into bite-sized pieces and place them in a greased 9x13 inch baking dish.
In a mixing bowl, whisk together eggs, heavy cream, garlic powder, salt, and pepper.
Pour the egg mixture over the croissants in the baking dish, making sure to cover all the pieces.
Sprinkle the diced ham or bacon, shredded cheese, and chopped green onions over the top.
Bake in the preheated oven for 35-40 minutes, or until the casserole is set and the top is golden.
Let the casserole cool for about 10 minutes before slicing and serving.