How to Make It
Preheat the oven to 375°. Butter a 9-by-13-inch glass baking dish. Arrange half of the challah in the dish; tear the slices to fit. Spread 3/4 cup of the jam on top; cover with the remaining challah.
Whisk the eggs, sugar, 2 1/2 cups of the milk and the vanilla and pour over the challah; press to soak and brush with 4 tablespoons of the butter. Cover with foil and bake for 24 minutes, removing the foil halfway through, until the pudding is set; remove from the oven.
Preheat the broiler. Blend the remaining 1 tablespoon of milk with the confectioners' sugar. Add the remaining butter and jam and stir until the glaze is smooth. Spread all but 1/4 cup of the glaze over the pudding and broil until the glaze is golden. Drizzle the bread pudding with the remaining glaze and serve.