Whip the butter for 1 minute on low speed and add egg yolk and whip on high speed for 5 minutes. Add the cheese, flour, milk powder and use a spatula to stir to mix into a non-sticky dough
Preheat oven to 330 F. Line baking sheet with parchment paper. Place a parchment paper or silicon mat on a working surface. Roll the dough out to about 1-inch thickness. Use a knife to cut the dough about 1-inch in width and then cut into individual about 3 inches long.Arrange these on the cookie sheet. Brush with egg wash and sprinkle with shredded cheese. Bake for 20 minutes or until golden brown.
Let the kastengel cool off on the baking sheet for 1 minute and then remove to cooling rack to let them cool down completely. Store in air-tight container and they can last up to one month
