Prepare an 8X8 baking dish by greasing it with 1 tablespoon of unsalted butter
Put cubed bread slices in a very large mixing bowl.
In a separate medium bowl, add the eggs, egg yolks, sugar, spices, and vanilla.
In a medium saucepan, add the cream and the milk. Heat over r medium-high heat until just simmering and then remove from heat.
Add cream mixture to egg mixture. Whisk constantly, while pouring the cream mixture into the eggs with a slow, steady stream
Pour mixture over the bread in the large bowl, folding so all pieces are covered in liquid and pressing down to make sure all are submerged. Let rest for at least 30 minutes up to 2 hours.
Preheat oven to 350F.
Using a slotted spoon, transfer all bread pieces to the greased pan. Pour the liquid at the bottom of the bowl on top of the bread pieces.
Place pan inside a roasting pan and pour boiling water into edges of the roasting pan to create a bain maire. Add water slowly ensuring that the water reaches 1/2 way up the dish, no more no less.
Bake until golden brown, about 40 minutes. Look for set edges and mostly set center, very very slightly jiggle is okay.
Let the dish cool for at least 20 minutes before slicing.