Bring the stock to a boil in a 2-liter saucepan, add the frozen peas, bring to the boil briefly, add half of the cream, remove from the heat and puree thoroughly. Then put back on the stove, bring to the boil again, add the remaining cream, season well with salt, pepper, nutmeg and cayenne pepper. Pour into four preheated soup bowls, place a teaspoon of creme fraîche in the middle, garnish with a little chives. Serve immediately!