First peel or clean the carrots and celery and slice them finely, cut the leek into small strips. Then heat the oil in the pan and add the vegetables and roast them lightly and add the semolina (amount depending on whether you want the soup to be thinner or thicker) and roast. Pour approx. 3/4 l of water and season with vegetable stock, salt and pepper. Simmer everything on a low heat until the vegetables are soft.