Peel and finely chop the onions and garlic. Clean the carrots and potatoes and cut into slightly larger cubes. It is best to grate the feta or cut it into very small cubes.
Heat the butter in a sufficiently large saucepan, add the onions and carrots and stir-fry for about 5 minutes. Braise the garlic very briefly. Deglaze with the chicken stock. Add the potatoes and simmer over low heat for about 20 minutes until the potatoes are cooked.
Then take the whole thing off the fire and puree. Then bring to the boil again, stir in the feta and let it melt. Season with salt, pepper, Worcestershire sauce and cayenne pepper and serve hot.