Preheat oven to 350°F. Pour the contents of the jar into a large bowl. Stir in 1 egg and 1/2 cup softened butter until combined. Drop dough by rounded teaspoons 2 inches apart onto an ungreased cookie sheet. Bake for 8 to 9 minutes or until lightly browned. Cool on cookie sheet for 2 minutes. Transfer cookies to a wire rack; cool.
To Make Ahead:
Store jar of mix in a cool, dry place for up to 1 month.
Layer cookies between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.