Preheat the oven to 200°C/400°F/Gas 6.
Make the filling
Heat the olive oil in a pan and fry the onion, garlic and pepper until softened. Add the potatoes, paprika and tuna and cook for 2-3 minutes, then pour over the stock. Simmer until the stock has been absorbed and the potatoes are tender, then season and set aside to cool.
Make the pastry
Sieve the flour and salt into a bowl. Heat the olive oil, wine and water in a pan until hand hot. Pour the warm liquid into the flour and knead until soft and elastic. Shape into a ball.
Turn out onto a floured surface and divide into 20 pieces. Roll each piece into a circle about 8cm in diameter.
Place a teaspoon of filling onto one half of the pastry and fold over the other half to enclose it, pressing down around the edges to seal it in. Repeat to make 20 little turnovers.
Bake on an oiled baking sheet for 15-20 minutes until golden brown.