Line baking sheet with parchment. Cook sausage, onion, caraway seeds, and fennel over medium heat, breaking sausage until no longer pink, for 6 to 8 minutes. Stir in flour until incorporated.
STEP 2
Off heat, stir in sauerkraut, cream cheese, mustard, and pepper until cream cheese melts. Cool for 10 minutes, then stir in beaten egg and chives. Divide into 36 portions, roll into balls, and transfer to sheet.
STEP 3
Place 1 cup flour in a shallow dish; beat remaining eggs in a second dish; place breadcrumbs in a third dish. Season breadcrumbs with salt and pepper.
STEP 4
Working in batches, roll balls in flour, dip in eggs, coat with breadcrumbs. Freeze on plates until firm, about 30 minutes.
STEP 5
Set wire rack in baking sheet. Heat oil in oven to 350 degrees. If balls flatten, reshape. Fry 12 balls at a time until golden, about 3 to 5 minutes. Transfer to rack. Return oil to 350 degrees and repeat.