Balkan Spaghetti

Cook spaghetti until al dente. Return the spaghetti to the still-hot saucepan and toss it, with two forks, with a tablespoonful of butter. See that every strand of spaghetti is coated with the butter. In a small pan, heat the oil and fry the chopped garlic in it for a minute or two, then add the tomato paste, and season with salt and a good grate of black pepper. Take the pan off the heat, add the yogurt and pour the mixture over the spaghetti.