GRANDMA WOMACK'S BUTTERHORN COOKIES

Steps:

• Cut butter into flour in a large mixing bowl with your fingertips. Add sour cream and egg yolk; mix thoroughly until a firm dough is formed. Shape dough into a large ball, cover with waxed paper or plastic wrap, and refrigerate until fully chilled, at least 2 hours.
• Preheat the oven to 375 degrees F (190 degrees C). Line 2 baking sheets with parchment paper.
• Combine sugar, walnuts, and cinnamon in a small bowl.
• Remove dough from the refrigerator and cut into 3 equal pieces. Roll 1 piece of dough into a circle. Sprinkle with 1/3 of the sugar mixture and press it into the dough. Cut into 12 wedges (like a pie) and roll each piece from the wide side to the tip to make a croissant-shaped cookie; place on the prepared baking sheets. Curl the tips of each cookie towards you to form a curved horn shape. Repeat with remaining dough and sugar mixture to form remaining cookies.
• Bake in batches in the preheated oven until golden brown, 20 to 25 minutes. Cool on the baking sheet for 1 minute before removing to a wire rack to cool completely.