Soak your clams in a large bowl filled with ice and water for at least 15 minutes—this will help them release some of the sand in the shells. Then scrub and rinse under cold water.
Heat olive oil in a large pot with a tight-fitting lid until shimmering, then add the chorizo and prosciutto. Brown, stirring occasionally until the sausage gets a little colour and the prosciutto starts to look like it’s crisping, about 5 to 7 minutes. Add the onions and peppers and continue to cook, stirring now and then, until the onions are soft but not brown, about 4 minutes. Add the garlic, and cook one minute more. Add the bay, pinch of saffron, paprika, tomatoes, and the white wine, stirring to deglaze the pan. Slowly add the prawn stock, then cook at a low simmer for about 20 minutes, until the tomatoes lose their tinniness and all the flavours have merged together.
Increase the heat to bring to a slow boil, add in the shrimp, hake and clams, cover with the lid, and cook about 5 to 10 minutes, shaking occasionally. Once the clams have opened, slowly stream in the cream and stir, then shower with fresh parsley.
Serve the cataplana right at the table, with bread, little fried potatoes, or white rice.