The batter will look lumpy, and it looks a bit strange as it bakes, but don't worry! You will still have a beautifully moist, delicious cake.
The ingredients list looks long and daunting, but it doesn't need to be followed exactly. If you don't have whey, buttermilk or regular milk will work fine, and you can just substitute in regular flour for the oat flour. I used meringue powder to keep the glaze from being too sweet, and you can find it at bakers' specialty stores (maybe even at some grocery stores?), but you can always just use more powdered sugar instead or make your glaze a little runnier. It's really up to you! —Melissa
Preheat oven to 350F. Position a rack in the center of the oven and preheat a baking pan on the lowest rack. Grease an 8” Bundt pan.
In a medium mixing bowl, combine flour, oat flour, baking powder, baking soda, nutmeg, ginger, and salt.
In the bowl of a stand mixer, beat together the butter, pumpkin puree, molasses, maple syrup, and sugars until small specks of butter remain. Add in the vanilla and eggs, beating well to fully incorporate. Drizzle in the whey and mix well. Add in half of the flour mixture and stir until almost fully incorporated, then add in the rest. Mix on low speed. Do not overmix.
Pour batter into the greased Bundt pan. Throw the ice cubes into the baking pan on the lower rack and bake the cake on the center rack for 40-45 minutes, or until a toothpick inserted in the middle comes out clean and barely moist.
In a small bowl, mix together the cream and ½ teaspoon vanilla extract. In a separate bowl, whisk together the milk, powdered sugar, and meringue powder to make the glaze.
Once the cake has baked, remove from the oven and place on a wire rack to cool. Pour the cream mixture over the cake, drizzling it over the entire surface. The cream should soak into the cake.
Cool in the pan for 15 minutes before inverting onto the wire rack, then cool completely before drizzling on the glaze. Serve immediately or refrigerate to allow the glaze to set.