Begin by shelling the prawns. Keep the heads and shells and place them in a medium saucepan with around 400ml of water along with parsley stalks and half an onion.
Next, thoroughly whisk together the two flours along with the baking powder. Briefly whisk in the soda water - don't worry if you have some lumps of flour left, and don't over whisk.
While this is happening heat up a sturdy saucepan roughly half full of sunflower oil to 170°C.
Dip the prawns and squid pieces into the batter and shake off excess. It should be the consistency of pancake batter.
Carefully place your seafood into your hot oil and fry until lightly golden and crisp, then remove with a slotted spoon and season.
To make the pasta sauce, fry the garlic along with the anchovies and chilli flakes until the garlic smells aromatic. Add the white wine and prawn head stock then reduce until thick and bubbling.
At this point make sure you have a lid or something to cover the pan to hand, then add the mussels and clams. Place the lid on top and steam until the shells have opened - if any look a bit stubborn give them a few more seconds as they might just need a bit more time! If they don't open at all discard them.
Toss the cooked linguine through the sauce, adding a few splashes of pasta water to the sauce to bring it together. Add the parsley.
Arrange the pasta and shells on a platter with the fried seafood (fritto misto) on top and serve forth!