Heat the butter and two tablespoons of the oil in a frying pan, and add the breadcrumbs. Fry, stirring every so often, over a medium-high heat until they’re golden and slightly toasted.
Put the linguine into a pan of boiling lightly salted water and cook until al dente (it always takes less time than it says on the packet). While the pasta is cooking, blot the prawns on both sides to dry them.
Add the rest of the olive oil to a large frying pan and cook the garlic until pale gold. Lift the slices out with a slotted spoon and reserve.
Leave the garlicky oil in the pan and set over a high heat.
Cook the prawns until they’ve turned from grey to pink and season them. Drain the pasta – reserving a little of the cooking water – and add it to the prawns. Add a couple of tablespoons of the reserved water and stir it with the juices and oil in the pan.
Add the cooked garlic, parsley, breadcrumbs, lemon juice and zest and toss everything together. Serve immediately.