Finely chop onions. Dice pumpkin. Melt butter in a pan, fry the onion until transparent and press the peeled garlic into it. Fry the pumpkin pieces for approx. 5 mins. Add stock, cover and leave to simmer on a medium heat for approx. 15 mins until the pumpkin is soft. Purée soup and season with curry powder, 1 pinch of sugar, 1 pinch of nutmeg and bay leaf. Then cover and leave to simmer on a low heat for a further 30 mins approximately. Take the pan off the hob, remove the bay leaf and stir in milk. Season with salt and pepper, and serve garnished with sour cream and chives.