The Dough: Place all ingredients in a mixer bowl, starting with the liquids. Knead for at least 9 minutes until the dough is uniform, smooth, and soft.
First Rise: Shape into a ball and place in a bowl until nearly doubled in volume.
Shaping: Divide the dough into pieces weighing 60-70g each (keep them uniform for even frying). Roll into smooth balls and place each on a small square of parchment paper.
Second Rise: Cover with lightly oiled plastic wrap (to prevent sticking) and then a towel.
Frying: Heat 2 liters of oil to 170°C–175°C. Carefully place the doughnuts into the oil with the parchment paper. Use tongs to pull the paper out once it releases.
Finishing: Fry for about 2 minutes per side and transfer to a cooling rack.
The Trap: Fill one doughnut with mustard and disguise it with a little dab of jam. Dust everything with powdered sugar before serving.