To prepare a sweet potato streusel casserole casseroles recipe, first you need to prepare the sweet potatoes. First, you'll need: Sweet Potatoes - Peel and cut into 1/4-inch cubes. Scoop out the flesh from the inside of the skin and place it in the bottom of an oven-proof casserole dish. Add the sugar, butter, eggs, vanilla, salt, cinnamon, and nutmeg. Pour the wet ingredients into the dry ingredients and stir to combine. Bake the casserole for 35 to 40 minutes, or until the top is brown and bubbly. Serve warm.