In a large mixing bowl, sift together the all-purpose flour, baking powder, baking soda, and salt.
Add the granulated sugar and whole milk powder to the dry ingredients and whisk to combine evenly.
Add the softened unsalted butter and vanilla bean powder to the dry mixture.
Using a hand mixer or stand mixer fitted with a paddle attachment, beat the mixture on medium speed until it resembles coarse crumbs and is evenly combined, about 2 to 3 minutes.
Transfer the cake mix to an airtight container or a large resealable plastic bag for storage.
To bake a cake using this mix, preheat your oven to 350°F (175°C).
In a separate bowl, combine 2 1/2 cups of the cake mix with 1 cup of water, 1/2 cup of vegetable oil, and 3 large eggs. Mix until smooth.
Pour the batter into a greased 9×13 inch baking pan or two 9-inch round cake pans.
Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool completely before frosting or serving.