Prepare two cookies sheets with lightly floured parchment paper.
Remove dough from fridge and set onto lightly floured surface.
Cut dough into 70 g pieces. (Use a kitchen scale to make each one even).
Fold edges of each piece inward upon itself to create a ball.
Roll ball on counter until smooth.
Place balls onto cookie sheets 2 inches apart.
Loosely cover cookie sheets with plastic bag.
Place in warm draft free location for up to 2 hrs until doubled in size.
Prepare your oil. Lay out a cooling rack covered in paper towels.
Fill a 2 inch deep iron skillet half way with vegetable oil.
Heat to 350 F (190 C), use a thermometer!
If your oil is too hot it will burn the outside of the doughnuts and leave the inside raw.
Gently remove doughnut balls from tray with a slotted spoon or spatula. Careful to prevent misshaping or deflating.
Cook 3-4 doughnuts at a time.
Place doughnut balls onto oil. They should float with half of each ball submerged.
Cook for 3 minutes and flip to cook the other side.
Doughnuts should be golden brown on each side with a light ring around the middle.
Place cooked doughnuts onto paper towels to absorb excess oil.
Let cool.
Roll or sprinkle doughnuts with a mixture of 1:1 granulated sugar and powdered sugar if desired.
Prepare your Buttercream!
Take a skewer and poke a hole in your doughnuts through to the center.
Insert tip of piping bag into hole and fill with buttercream.
Squeeze until pressure pushes tip out, leaving a little on the outside for decoration.