Heat the olive oil in a large pot over medium heat. Add the sliced onion and cook until it softens, about 5 minutes. Stir in the minced garlic and cook for 1 minute more.
Add the smoked paprika and ground cumin to the pot. Stir for 30 seconds to toast the spices, then pour in the diced tomatoes with their juice and the fish stock.
Add the bay leaves, sliced potatoes, piri piri sauce, salt, and black pepper. Bring the mixture to a simmer, then cover and cook for 15 minutes until the potatoes begin to soften.
Gently place the fish chunks into the pot. Simmer uncovered for 8 to 10 minutes until the fish flakes easily and the potatoes are tender.
Remove the bay leaves. Ladle the stew into bowls and sprinkle with chopped parsley before serving.