Cream the butter and sugars until light and fluffy (at least 4 minutes.)
1 cup granulated sugar, 1 cup powdered sugar, 1 cup butter
Add in the oil and eggs and vanilla and mix well.
1 cup oil, 2 eggs, 1 tsp vanilla
With the mixer on low, add the rest of the ingredients one at a time until mixed.
1 tsp baking soda, 1 tsp cream of tartar, ½ tsp salt, 4 cups flour
Chill the dough for at least an hour so it can be rolled into balls easily.
Roll into balls at least 2” around (about 2 heaping Tbsp each) and place on a cookie sheet.
Press each cookie ball down until it’s ½” thick with the bottom of a glass dipped in granulated sugar. The cookie dough circle should still be about 2” wide.
Bake at 375 for 9-10 minutes. Remove from oven and leave on the pan at least 5 minutes to finish baking. Cool on wire racks.
Notes
Ideally, you don't want the edges of the flattened cookie dough to be higher than the center-the cookies should be perfectly even all the way across.Try to use a glass that's 2" across the bottom and then don't press the dough out beyond the edges of the glass.The larger the amount of dough in each cookie ball, the chewier/softer the center will be. If you want truly crispy cookies from edge to edge, simply use a bit less dough.