Mix flour, salt, vinegar and oil to a smooth dough. Cover the dough and leave to rise in a warm place for about 20 minutes. Put the tuna in a bowl. Drain and coarsely chop the olives. Clean and wash spring onion and cut into fine rings.
Add cheese, olives and spring onion to the tuna. Mix everything, season with pepper. Roll out the dough on a floured work surface. Cut out 18 circles (6 cm Ø). Place 1 teaspoon of filling on each circle and fold over. Press the edges together with a fork. Place the dough pockets on a baking tray lined with baking paper. Mix egg yolk and milk. Coat the dumplings with the mixture and bake in a preheated oven (electric: 225 ° C/ gas: level 4) for 15 minutes.
Place 1 teaspoon of filling on each circle and fold over. Press the edges together with a fork. Place the dough pockets on a baking tray lined with baking paper. Mix egg yolk and milk. Coat the dumplings with the mixture and bake in a preheated oven (electric: 225 ° C/ gas: level 4) for 15 minutes. Serve filled dumplings hot
With 10 people: