Step 1

In a large bowl with an electric mixer, beat butter and sugar until fluffy. Add egg and vanilla and beat until well combined. Add potatoes and buttermilk and beat until smooth. Add 2 cups flour, the baking powder, baking soda, salt, and cinnamon and beat just until evenly mixed. Do not over mix.

Step 2

Generously dust your countertop with flour. Place dough on countertop and turn to coat with flour.

Step 3

Gently press dough out with your hands to 1/2-inch thickness and cut into rounds using a 3-inch donut cutter or biscuit cutter and 1-inch bottle cap for center hole. Gather scraps of dough and gently press out again as needed until all dough is used.

Step 4

In a soup pot, heat shortening over medium heat to 375 degrees, using a thermometer. Working in small batches, cook donuts 2 to 3 minutes per side or until puffed and golden brown on both sides, turning once during cooking. Transfer to a paper towel-lined platter.