1. Generously butter a cookie sheet. In a large saucepan over high heat, cook sugar, water, and corn syrup until mixture reaches 280 degree F on a candy thermometer. Slowly add nuts and stir until temperature reaches 300 degree F. Turn off heat. Carefully stir in butter and vanilla until blended. Add baking soda, and stir vigorously but cautiously. Pour mixture onto prepared cookie sheet and spread as thinly as possible with a wooden spoon. Cool completely, about 15 minutes. Break cooled candy into pieces and then chop to make topping. Store in an airtight container. Makes about 2 pounds.