- Preheat oven to 375 degrees.
- In a bowl, beat together the butter, oil, and both sugars.
- Add eggs and vanilla, beat in until well combined.
- Add in baking soda, cream of tartar, and flour. beat until just combined.
- Using a cookie scoop, scoop dough onto an ungreased baking sheet. Bake at 375 for 8 to 10 minutes until lightly browned. Cool on wire racks. Makes about 5 dozen.