1. Heat oven to 350°F. Lightly grease cookie sheet or line with parchment paper.
2. Beat butter, granulated sugar, brown sugar, vanilla and salt in large bowl until blended. Add eggs; beat well. Stir together flour, baking soda and cream of tartar; gradually add to butter mixture, beating until blended. Stir in toffee bits. Drop by heaping teaspoons onto prepared cookie sheet.
3. Bake 8 to 10 minutes or until lightly browned. Cool slightly; remove to wire rack. Cool completely. Makes about 6 dozen cookies.