Heat the olive oil in a large, deep-sided frying pan and brown the pork over a medium-high heat for 2–3 minutes, turning occasionally. Add the chorizo, cook for 1 minute, then transfer all the meat to a plate and set aside.
Cook the pepper and onion in the same pan for 3–4 minutes, until beginning to soften. Add the garlic and mushrooms and cook for a further 2–3 minutes, to soften slightly.
Stir in the paprika and potatoes and heat for 1 minute. Add the tomatoes and stock and simmer for about 12 minutes, until the potato is almost tender.
Return the meat to the pan and cook for 5–6 minutes more, until the pork is cooked but still juicy. Season to taste.
Scatter the goulash with chopped parsley. Serve in dishes with cooked long-grain rice and dollops of soured cream.