Peel and cut the potatoes into small pieces (the smaller you cut, the easier and faster it cooks).
Put them in a pan and cover them with water.
Cook it for 20-30 minutes or until the potatoes are soft enough.
While the potatoes are cooking, cut the fish (if needed) to smaller pieces.
Heat the oil.
Mix the flour, the cold sparkling water, the eggs and the spices.
Cover the fishes with the extra flour, so the batter will stick to them.
Dip the fishes into the batter.
Fry them on high heat, turn them every few minute until they turn golden color.
When the potatoes soft enough, drain the excess water off them.
Add the salt and the pepper, then mash the potatoes.
When it's well mashed, add the sour cream and mix it well.
Serve it with some more sour cream and a little more pepper. * Optional