Preheat oven to 180C or 350F. Grease a 13” x 9” baking dish and set aside.
Cook broccoli:Place broccoli florets in a steamer. Sprinkle with salt. Steam for about 5 minutes or until crisp-tender.
White sauce:Heat butter in a frying pan over medium heat. Add garlic cloves. Sauté, stirring occasionally, for about a minute. Add dijon mustard, and sauté, stirring, for about a minute. Add cream and nutmeg. Season with salt and pepper. Cook, stirring occasionally, for 3-4 minutes or until thickened. Remove from heat. Leave to cool. Stir in parmesan cheese.
Buttered breadcrumbs:Remove the brown ends from the bread slices. Place in a food processor, and process to crumbs. Set aside.Heat butter in a frying pan over medium heat. Add breadcrumbs. Stir fry for about 10 minutes or until browned. Set aside.
Make broccoli gratin:Place cooked broccoli in the prepared baking dish. Pour white sauce on top. Sprinkle with buttered breadcrumbs. Transfer to oven. Bake for about 20-30 minutes.