French Toast Bread Pudding with Pumpkin Maple Syrup

Name: French Toast Bread Pudding with Pumpkin Maple Syrup
Ingredients: 1/2 cup creme fraiche or sour cream; 2 tablespoons confectioners' sugar; 1/4 teaspoon pumpkin pie spice (see Cook's Note); Soft butter, for the baking dish; 5 large eggs; 1 1/4 cups granulated sugar; 2 cups heavy cream; 2 cups whole milk; 1 teaspoon ground cinnamon; 8 cups (1-inch) cubes rich bread, such as challah or brioche loaf, preferably slightly stale, about 10 ounces; 1 cup pure maple syrup; 2/3 cup solid-pack pumpkin puree; 1/4 cup heavy cream