Wash the potatoes. Cook in boiling water with caraway and bay leaf for about 20 minutes, drain and let cool. Peel the potatoes and cut into large cubes. Let the strudel dough sheets rest at room temperature for about 10 minutes
Peel onion and garlic and cut into fine cubes. Heat the oil in a pan and fry the minced meat in it while turning, add the onion and garlic and fry briefly. Season the minced meat mass with salt and pepper, remove from the heat and let it cool down
Wash, clean, seed and cut the tomatoes into large cubes. Crumble the feta cheese, mix it with the tomatoes, season with salt, pepper and lemon juice. Mix potato cubes, minced meat and tomato mixture and season again with salt and pepper if necessary
Melt the butter. Spread out 1 sheet of baking paper on the work surface and lay 4 sheets of filo pastry slightly overlapping to form a rectangle (30 x 70 cm) so that the pastry is centred on the baking paper, brushing the sheets with melted butter. Place the 5th sheet of dough crosswise in the middle of the rectangle. Wrap the remaining filo pastry well, store in the refrigerator and use it for other purposes as soon as possible
Place the minced potato mixture on the edge of one of the long sides so that a good 15 cm wide strip remains free on both sides. Whip this to the middle over the filling and roll everything up into a strudel. Place the strudel diagonally on a baking tray using the baking paper. Brush the strudel with egg yolk and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 15-20 minutes until golden yellow