Grease a 15x10x1 inch baking pan with 1 Tbsp butter; set aside. In a heavy 3-quart saucepan, melt the remaining butter. Add sugar, corn syrup, and salt; cook and stir over medium heat until a candy thermometer reads 295 (hard-crack stage). Quickly pour into prepared pan. Let stand at room temperature until cool; about 1 hour.
In a microwave, melt chocolate chips; spread over toffee. Sprinkle with pecans. Let stand for 1 hour. Break into bite-sized pieces. Store in an airtight container at room temperature. Yield: about 2 pounds