Greae baking dish and fill with bread cubes to the top.
To make the custard, whisk 6 eggs in a large bowl. Add 1 cup sugar, 4 cups milk, vanilla, cinnamon, and nutmeg. Whisk together.
Pour mixture over bread cubes in baking dish. Push down bread to absorb all liquid. Set a side for 20 minutes.
Preheat oven to 350 degrees.
Cover baking dish with tin foil and bake in oven for 20 minutes. Remove tin foil and place back in oven for an additional 20-25 minutes, until golden brown.
To make the vanilla sauce, in a medium sauce pan, melt better. Add brown sugar, flour, egg, milk, and vanilla, and whisk together. Cook for 10 minutes while continually whisking.
Pour over bread pudding. Add ice cream.