Add buttermilk to the mixture and stir to combine.
Work the dough until everything is well combined. The dough will be sticky, but that is ok. I usually knead by hand but a stand mixer with a dough hook can be used as well.
Cut the dough into 12 equal pieces. Flour the surface that you are working on and roll each dough piece out.
Place equal amounts of mashed potatoes onto each dough piece. Seal the edges of each one, pinching tightly.
Carefully roll out each one into a flat piece. You may need to continue flouring the surface you're working on if it's overly sticky.
Preheat a skillet filled with oil to medium heat. Then, fry each pastry until it's golden brown. Serve immediately!