Grease a 9 x 13-inch baking pan with butter. Tear bread into chunks (or cut into cubes) and evenly distribute in the pan. In a medium sized bowl, mix together eggs, milk, cream, sugar, and vanilla. Pour evenly over the bread. Cover tightly and store in the fridge for several hours or overnight. In a separate bowl, mix flour, brown sugar, cinnamon, and salt. Add nutmeg if desired. Add butter pieces and cut them into the dry mixture until mixture resembles fine pebbles. Store in a Ziploc in the fridge. When you're ready to bake the casserole, preheat oven to 350° F. Remove casserole from the fridge and sprinkle crumb mixture over the top. (If you're using fruit, sprinkle on before the crumb mixture.) Bake for 45 minutes for a softer, more bread pudding texture. Bake 1 hour or more for a firmer, less liquid texture. Scoop out individual portions. Top with butter and drizzle with maple syrup.