In a frying pan, soften the chopped leek and mushrooms in a little cooking spray over medium heat.
Meanwhile, in a wok over a medium heat, brown the mince. Add enough of the stock to cover it, and let cook it off. Once the stock has gone, add the smoked paprika, garlic and oregano and mix well. Cook for 2 to 3 minutes, stirring constantly, so it doesn't stick to the pan.
By now the leeks and mushrooms should have softened, add them to the mince along with the chopped tomatoes and the rest of the stock, season with salt and pepper and simmer over a medium heat until dry enough to put into a pitta.
Put the pitta under the grill following the packet instructions. Serve the mince with the grilled pitta. For a complete meal, serve with your choice of salad and/or chips.