You can prepare this dough in advance: it keeps for 2 to 3 days in the refrigerator, or freezes very well. Simply take it out the day before and let it thaw slowly in the refrigerator.

In a bowl, mix the flour, salt, vinegar, and butter cut into large pieces. Work lightly with your fingertips, then gather everything into a ball with a little very cold water.

Don't try to fully incorporate the butter into the dough, that's the whole secret!

Don't knead the dough, and avoid adding too much water, just enough to bring it together.

If it's warm, place the dough in the refrigerator between each turn of folding.

Roll out the ball into a long rectangle about 1 cm thick. Fold it in three by folding one side towards the center, then the other over it.

You have just completed a single turn.

Turn the dough a quarter turn so that the folds are always on the right. Repeat the operation twice to obtain three single turns in total (roll out, fold in three, turn).

Heat 2 tablespoons of olive oil in a pan. Add the coarsely chopped onion, then sauté over low heat.

Then incorporate the finely grated carrots. Season with salt and pepper and cook, stirring regularly, until the carrots are very tender.

Let it cool, then add the flaked tuna, grated cheese, and oregano.

Roll out the dough to a thickness of about 4 mm, not too thin. Cut out 8 cm circles using a cookie cutter or a glass. Place them on a tray, then put them in the refrigerator while you continue to cut out all the dough.

Place a small roll of filling in the center of each disc (about a heaping tablespoon).

Brush half of the circle with egg yolk, then close to form a turnover.

Gently score the top of the turnovers with a knife. This is optional, but it gives a nice finish.

Place the formed turnovers on a tray, and put them back in the refrigerator while you finish the others.

"You can crimp the edges of the turnovers for a neater finish (optional). Then place them on a baking sheet lined with parchment paper and chill in the refrigerator for 15 minutes to firm up the dough.

Brush the turnovers with egg yolk and sprinkle them with poppy seeds. To better visualize the technique, don't hesitate to watch the video.

Place a few drops of water on the baking sheet with your fingertips to create steam, then bake the turnovers until they are golden brown, about 25 minutes.

Once cooked and golden brown, place them on a wire rack. Serve them hot or let them cool if you want to store them.