Using a stand mixer, add in the flour, baking powder and salt. With the mixer on low, add butter and mix until butter looks like the size of peas.
In another smaller bowl, add buttermilk and egg and lightly beat together. With the mixer on low, add the buttermilk mixture to the flour mixture until moist. In another bowl, lightly toss the cheese with some flour and add to dough and mix until everything is combined.
Place dough on a floured and clean surface and knead dough a few times. Then roll the dough into a rectangle shape with a floured rolling pin. Using a round cookie cutter (or any shape), cut out biscuits. Roll the scraps again and continue.
Place biscuits on a non-stick baking sheet and brush with egg wash.
Bake at 425 degrees F for about 20 minutes (or until lightly browned and cooked through).