Potato dough: dumplings, noky, gnocchi

Why

A cooked potato is a cluster of cells full of swollen starch (see the Mashed potatoes card); when long kneading or blending ruptures the cells, the released starch forms a sticky mass with the water from the potatoes, more flour then gets added, and the dumpling turns out tough and gummy. Floury potatoes of cooking type C, or B, have more starch and less water and give a supple dough with less flour, whereas watery waxy potatoes of type A thin the dough; that is why the potatoes are boiled in their skins or baked and left to steam off and cool before use. Finished dough softens and gets sticky as it stands, and the more flour then goes in, the tougher the dumpling, so it is worked quickly and cooked at once. In the water it keeps its shape when the water only simmers and the surface sets quickly, whereas a hard boil and long cooking wear the surface away and the dumpling or gnocchi falls apart. Green patches, eyes and sprouts of potatoes contain bitter, toxic glycoalkaloids (solanine), so the German BfR advises removing them generously.

How to do it

• Choose floury potatoes of type C, or B; boil them in their skins or bake them, peel and let them steam off and cool, even a day ahead in the fridge.
• Cut out green patches and eyes generously; do not use green, shrivelled or heavily sprouted potatoes, or potatoes that taste bitter.
• Grate the potatoes finely or put them through a ricer, do not blend them; add egg, salt and flour and bring the dough together quickly, just until smooth and holding its shape.
• Add the flour gradually: first cook one small test dumpling or gnocchi and add more flour only if it falls apart.
• Cook shaped dumplings and gnocchi at once, in small batches, in salted, gently simmering water; lift gnocchi out shortly after they float.
• Take a cooked dumpling out at once, pierce it and slice it with thread or a sharp knife; move gnocchi straight into the sauce or melted butter so they do not stick together.

If it goes wrong

Firm up sticky dough with only a small amount of flour or semolina and shape it at once, as more kneading makes it worse. If the test dumpling falls apart, add a little flour or egg; if a whole dumpling falls apart in the water, cook the rest of the dough as small gnocchi or fry it as pancakes. Tough, gummy dumplings will not soften again: slice and fry them in butter, perhaps with eggs or cabbage, and next time use less flour and knead less.