Drain the sauerkraut really well and chop it finely. Excess liquid is the enemy of crispness.
Chop the onion as small as you can – you want it to melt into the batter.
Add everything to a bowl: sauerkraut, onion, milk, flour, eggs, baking soda, spices, and that small pinch of sugar. Mix until combined.
The batter should be thick but spoonable – like sour cream. If it feels too stiff, add a splash of milk.
Heat oil in a pan over medium heat.
Spoon the batter onto the hot pan, flattening slightly.
Fry until golden and crispy on both sides. Don’t rush them – good fuczki like a little patience.
Transfer to a plate and repeat until the batter is gone (or until people start eating them straight from the pan).
Serve with sour cream mixed with salt, pepper, lots of dill and ranch seasoning, mushroom sauce or more sauerkraut