If you're doing Meatless Monday, the recipe below is about to become your new best friend. This casserole combines broccoli with tons of gooey cheese for a moreish meal that's nevertheless rich in nutrients – and, of course, in flavor.
But this recipe is sure to become a staple for another reason: it's the perfect way to use up odds and ends you may have lying around. Stale bread and broccoli stems that have been discarded when you only needed florets both find their way into this dish. Whenever you use broccoli in another recipe, freeze the stems, and when you have enough, defrost, make, and bake!
Break all of the florets off of the heads of the broccoli. Reserve 2 cups of florets. Roughly the remaining florets and stems.
Heat the butter in a pot over medium heat. Add the onion and sauté until slightly browned, about 10 minutes. Add the garlic and cook until fragrant, about 1 minute, then add the chopped broccoli and stir to combine. Add about 2 tablespoons of water and cover to steam for about 4 minutes.
When the broccoli is cooked, transfer it to a blender or food processor. Process until smooth and creamy, adding a bit of the milk if needed to get the blades to move.
Transfer the broccoli purée to a bowl. Add the eggs, one at a time, the remaining milk, the nutmeg, the pepper, and the salt. Add about half of each of the cheeses to the mixture and stir well to combine.
Arrange the bread in a buttered 9x13-inch casserole dish. Pour the broccoli mixture over the top, and allow to sit for about 10 minutes. Top with the reserved broccoli florets.
Bake for about 20 minutes, then add the remaining cheese. Continue baking for about 20 more minutes, until the broccoli custard is set. Allow to cool slightly before serving.
