Grease a 12x16 cookies sheet and lay challah slices flat in one layer.
Mix all custard ingredients and pour over the bread.
Cover tray and refrigerate over night.
Uncover in the morning and turn over each slice.
Dot the slices with the diced butter.
Bake uncovered in a preheated 350 degree oven for approx 45-50 minutes.
Serve with fresh whipped cream, berries and syrup!