For creamy baked mac and cheese, place the baked mac and cheese in the oven under the broiler for 2-3 minutes, watch carefully. You want the cheese to melt and the tops to toast, but not burn. For more a traditional "firm" baked mac and cheese recipe, turn the oven to 400 degrees, and bake for 20 minutes until the tops are golden. Once out of the oven, sprinkle the remaining green onions and bacon over the top and serve warm.