For the dough, place the flour in a bowl and mix with salt, 4 tbsp oil and 150ml lukewarm water. Knead to a smooth, supple dough. If necessary, add some more flour or water. Shape the dough into a ball, brush with the remaining oil and leave to stand for 30 minutes, covered with a damp cloth.
For the filling, peel and finely dice the onion and garlic.
Wash, deseed and dice the pepper.
Peel and finely grate the carrot.
Wash and dice the courgettes.
Heat the oil in a frying pan, fry the mince, breaking up with a wooden spoon until browned all over. Add the onion, garlic, pepper and carrot and fry for 5 minutes, stirring. Season with salt, pepper, cumin, paprika and chilli powder. Stir in the tomato paste and cook, stirring, for 1 minute.
Add the wine and allow to bubble. Add the stock, courgettes and the parsley. Continue stirring until the liquid has almost evaporated, then set aside.
Cut the mozzarella into small cubes.
Stir half of the mozzarella and the ajvar into the mince, season to taste and leave to cool.
Sprinkle a tea towel with flour, place the dough in the middle and roll it out into a rectangle. Carefully pull and stretch the dough from the centre over the back of your hand to about 30 x 40 cm. Spread the mince mixture over two thirds of the dough. Roll up the dough using the towel to help.
Preheat the oven to 180°C (160°C fan, gas 4). Line a baking sheet with baking paper. Place the strudel on the sheet, brush with butter, sprinkle with the remaining mozzarella and bake in the oven for 30-35 minutes. Take the strudel out, cut into slices, arrange on plates and serve.