Preheat oven to 375F and lightly grease a 12-mold donut pan.
In medium-sized bowl, whisk together flour, sugar, Jif Peanut Powder, cornstarch, baking powder, baking soda, and salt.
In separate large bowl, combine melted butter, greek yogurt, lightly beaten egg and vanilla extract. Stir together until well-combined, then add milk and stir again until combined.
Add dry ingredients to wet and stir until just combined.
Pour batter into a large ziploc bag and snip off the corner of the bag for a makeshift piping bag (alternatively you can spoon the batter into the molds).
Pipe the batter into the donut pans, filling each mold ⅔ of the way full.
Bake for 10 minutes. Allow to cool for several minutes and enjoy fresh. If covering with frosting, allow donuts to cool 10-15 minutes before glazing.