When you've finished cutting out the donuts, cover with plastic wrap and let sit in a warm spot to proof until they almost double in size. This should take about 5 to 20 minutes. Be sure to test the dough at 5 minute intervals, tough the dough lightly with your fingertip. If the dough springs back immediately, it needs more time. If it springs back slowly, it is ready. If it doesn't spring back at all, it has overproofed -- you can punch it down and reroll it at once.