In a mixing bowl, combine all ingredients except for currants. Mix on slow speed with a dough hook for approximately 3 minutes, until ingredients are incorporated. Increase the speed of the mixer to medium speed and mix for 5–6 minutes to develop the dough.
At the end of mixing, add currants and mix on slow speed until evenly distributed. Allow dough to proof at 27C for 1 hour. Roll dough out to thickness of about 1”. Cut with floured doughnut cutter.
Place doughnuts and holes on parchment-lined pan. Brush with melted butter and allow to proof at 27C for fourty-five minutes to 1 hour.
Bake at 180°C for 12–15 minutes. While hot, brush with melted butter, then roll in granulated sugar. Place each doughnut hole on the doughnut. Dust generously with powdered sugar.