Put the chicken pieces in a bowl and sprinkle over the paprika, salt and plenty of freshly ground black pepper. Rub the seasoning into the meat and set aside.
Heat the oil in a large frying pan and fry the onions and peppers with the thyme and bay leaves for 3 minutes, while stirring. Add the chicken and seasoning and cook for another 3 minutes, turning the chicken regularly until it is starting to colour. Add the chorizo and garlic and fry for 2 minutes more. Add the tomatoes and cook for 5 minutes or until they are softened and juicy, stirring regularly.
Tilt the pan so that the liquid runs to one side and sprinkle the flour over the vegetables, chicken and chorizo. Stir it in quickly, then set the pan level and stir the cooking liquor into the flour. Doing it this way should prevent little clumps of flour – but don’t worry if you do have a few, no-one will notice. Add more salt and pepper if necessary and continue to cook for one minute, stirring until the sauce thickens. Remove from the heat and tip everything into a roasting tin or ovenproof dish, measuring about 25x30cm/10x12in and at least 4cm/1½in deep. Leave to cool.
For the pastry, pulse the flour, baking powder, salt, butter and egg yolk in a food processor until the mixture resembles breadcrumbs. Slowly pour in the water with the motor running, blending until the mixture just comes together as a dough (you may not need to use all of the water). Form the dough into a ball.
Preheat the oven to 200C/400F/Gas 6.
Roll the pastry out into a rectangle about the same size as the tin. Place it over the pie filling and tuck the sides of the pastry down around the filling. Brush with beaten egg or milk to glaze.
Bake for about 30 minutes or until the pastry is golden and the filling is hot.