Peel and dice the potatoes. Peel and finely chop the shallot and garlic. Saute the shallot and garlic in hot oil until translucent. Add the peas and potatoes. Deglaze with the broth. Let simmer for about 20 minutes, until the contents of the pan are softened. Add the basil and puree. Season with salt, pepper and a pinch of nutmeg.
Garnish the soup with sour cream and basil. Serve hot.