Cook the pasta in boiling, salted water until just tender, following package directions, drain. Grind 3/4 cup of walnuts in food processor. In large frying pan, sauté ground walnuts and garlic in butter for 1 minute over medium high heat. Add the pasta to nut and garlic mixture, tossing well. Place the pasta in warmed serving bowl, sprinkle with remaining walnuts. Heat the sour cream in saucepan over low heat, stirring constantly, do not boil. Serve pasta with heated sour cream separately. Serves 4