Whisk the buckwheat flour, 00 flour and fine salt together in a bowl. Beat the egg with 110 ml milk, pour it in and mix with a fork, then knead on the counter for 2 minutes until the dough is stiff and slightly tacky. If it's crumbly, add milk 1 tbsp at a time. If it sticks to your hands, knead in flour by the spoonful.

Wrap the dough or cover the bowl and rest for 20 minutes. While it rests, fill the 26 cm / 10-inch stockpot with 3 L water, add 1 tbsp coarse salt, bring to a boil, and prep the potatoes, cabbage and cheese.

Dust a board with 00 flour. Roll the dough into ropes about 1 cm thick and cut them into 1.5 cm pieces. Toss the pieces in a little flour so they don't stick together. A rope that slumps or smears means the dough needs more flour.

Drop the potatoes into the boiling water and cook for 4 minutes. Add the cabbage and cook for 4 minutes more, then add the dumplings and reduce to a steady simmer for 4 minutes, until they float and a cut piece is evenly grey-brown with no pale center.

While the dumplings simmer, melt the butter in the 30 cm / 12-inch deep sauté pan over medium heat. Add the garlic and sage and cook for 2 to 3 minutes, until the butter foams, the sage turns crisp and the garlic is pale gold. Remove from the heat if it's ready early.

Lift the dumplings, potato and cabbage into the pan with a slotted spoon, letting a little water come along. Add the Casera and half the Parmigiano, set over low heat, and toss for about 1 minute until the cheese melts into a glossy coating. Season with pepper and serve within 10 minutes with the remaining Parmigiano.