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