For the dough, knead flour, oil, salt, egg and water on a floured pasta board to a smooth pasta dough, roll it in a cling film and let it rest for at least 1 hour.
Meanwhile, for the filling, sauté the chopped onion in butter, add the cooked and strained potatoes and mix in the chopped wild garlic, egg yolk and breadcrumbs. Season with salt and pepper to taste.
Roll out the dough thinly on a floured rolling pin and cut out pieces of dough about 8 cm in diameter with a round cutter. Place a heaping teaspoon of filling in the center of the dough, brush the edge with beaten egg, fold and press firmly with a fork.
Place in a pot of boiling salted water for a few minutes until the pastries float to the surface. Remove the pastries from the water with a sieve ladle and serve.