Thinly slice the leek and garlic.
Heat the oil in a large frying pan and gently sauté the leek, under cover, for about 5 minutes, then add the garlic and stir for a minute.
Add the green beans and the wine. Let it bubble for a few seconds and reduce the liquid until the pan is almost dry.
Add the stock, bring to the boil, put a cover on and cook for 2 minutes.
Place the prawns on top of the vegetables, scatter the dill around them and drizzle with the lemon juice. Season with salt and pepper.
Put the lid on again, then cook for 3 minutes over medium-high heat until the prawns change colour.
Serve immediately.