Spread over the bottom of a 13 × 9-inch baking dish:
Cut into ½-inch-thick slices:
Arrange the slices almost upright in tightly spaced rows in the prepared dish. Tuck between the slices:
Whisk in a large bowl until frothy:
Pour the liquid over the bread and let stand for 1 hour, periodically pressing the bread down with a spatula to wet the tops of the slices.
Preheat the oven to 375°F.
Bake the pudding until the top is puffed and lightly browned, about 1 hour. When it comes out of the oven, cover with:
Let cool on a rack for 30 to 60 minutes, then cut into squares and serve.