Preheat oven to 375°F.\n\n1. Measure flour and salt into bow. Cut in butter using a pastry blender.\n2. Stir in egg yolk and sour cream.\n3. Shape into a ball and chill.\n4. In the meantime, blend sugar, nuts and cinnamon in a small bowl.\n5. When dough is cold, divide into 3 portions. On a floured surface, roll each into a 12-inch circle and sprinkle with nut mixture.\n6. Cut into 12 pie shaped wedges. Roll up each wedge, starting at the wide end and tucking the end under.\n\nPlace on a baking sheet covered with parchment paper. Bake for 20-30 minutes. Allow to cool and frost with glaze, if desired.\n\n**Butterhorn Glaze:**\n\n- 1 Cup Powdered Sugar\n- 2 Teaspoons Milk\n- ¼ Teaspoon Vanilla\n\nMix in a small bowl until smooth. Drizzle over cooled butterhorns.