1-pound loaf cinnamon bread, cut into 1-inch cubes
2 cups heavy cream
1 cup plus 1 to 4 tablespoons whole milk, divided
1 cup (packed) dark brown sugar, divided
5 large eggs
2 teaspoons apple pie spice, divided
2 teaspoons vanilla extract, divided
¼ cup unsalted butter
2 tablespoons all-purpose flour
1 ¾ pounds apples, peeled, cored, and diced
¾ cup water
½ cup chopped walnuts
1 ½ cups powdered sugar
Preheat the oven to 350° F. Grease a 9-by-13-inch baking dish with butter or oil.
Place the bread cubes in the prepared baking dish and spread them out in an even layer.
In a large mixing bowl, whisk together the cream, 1 cup of the milk, ½ cup brown sugar, eggs, 1 teaspoon of the apple pie spice, and 1 teaspoon of the vanilla. Pour this mixture over the bread cubes in the baking dish, pressing down lightly to make sure all of the bread gets saturated with the mixture. Let stand for at least 15 minutes, or cover and refrigerate as long as overnight.
Meanwhile, in a medium saucepan over medium heat, melt the butter. Sprinkle the flour over the melted butter and cook, whisking, for a minute or two. Stir in the remaining ½ cup of brown of brown sugar and the apples, the remaining 1 teaspoon of apple pie spice, and the water. Cover the saucepan and cook over medium heat, stirring occasionally, for 10 to 15 minutes, until the apples are tender. Remove from the heat and let cool for a few minutes.
Spread the apple mixture over the top of the bread in the baking dish and then sprinkle the nuts over the top.
Bake in the preheated oven until the pudding is puffed up and golden brown on top, about 30 minutes.
Remove the pudding from the oven and set aside to cool while you make the glaze.
In a small bowl, mix together the powdered sugar and 1 tablespoon of the remaining milk along with the remaining teaspoon of apple pie spice and the remaining teaspoon of vanilla. Add additional milk if needed for consistency. Drizzle the glaze over the warm bread pudding and serve immediately.