Fill and boil your kettle. Use a sharp knife to separate the octopus tentacles from each other, then cut them into 1 or 2-inch chunks. Slice the head into similarly-sized pieces. Next, slice the onion, and cut the prepared peppers into small-ish chunks, then place a deep saucepan (one which has a lid) over a medium heat and add the 2 tbsp oil. When hot, add the onion and pepper and cook, stirring, until just starting to brown. Crush in the garlic cloves and cook for another minute, stirring, then add the white wine (if using) and let it sizzle for a few seconds. Stir in the paprika and the octopus pieces, then sprinkle over the stock powder and add the tomatoes. Pour in 300ml boiled water from the kettle, then turn the heat down immediately to a low simmer, put the lid on the pan and cook for about an hour, or until the octopus is tender when pierced with a fork or sharp knife. Keep an eye on the liquid levels, topping up from the kettle if the pan seems dry.

When the octopus is tender, take the lid off the pan, add the prepared potatoes and cook for another 15 minutes, or until the potatoes are cooked through (again, keep an eye on the liquid levels). Stir in the sliced olives and season to taste with salt and pepper. Scatter over the parsley, then serve.