Heat the oil in a saucepan and sauté the finely chopped garlic and ginger in it. Halve the chilli and cut into rings.
Put half of the chilli pepper in the saucepan and sauté. Add the turnip and potato cubes and sauté briefly. Dust with curry. Pour in the stock and milk and cook for about 15 minutes.
Puree the soup finely and season with the spices and lemon juice. Serve sprinkled with the remaining chili rings.