Wild garlic & nettle soup

Name: Wild garlic & nettle soup
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: British
Ingredients: 1 tbsp rapeseed oil plus extra for drizzling; 25g butter; 1 onion finely diced; 1 leek finely diced; 2 celery sticks, thinly sliced; 1 carrot finely diced; 1 small potato peeled and diced; 1.2l good-quality vegetable stock; 300g young nettle leaves; 200g wild garlic leaves (keep any flowers if you have them); 3 tbsp milk