How to Make It
Warm oil in a large skillet over medium heat. Add sausage and cook, stirring occasionally, until browned, about 4 minutes. Remove to a plate using a slotted spoon.
Melt butter in same skillet over medium heat and add onion. Cook, stirring, until translucent, about 4 minutes. Stir in apples and cook until tender, about 5 minutes. Return sausage to skillet, along with sauerkraut, cider vinegar and sugar. Stir to combine. Cook, stirring, until warmed through, about 2 minutes. Season generously with pepper, then serve.