- 2 cups white sugar
- 1/2 cup butter, softened
- 1/2 cup vegetable oil
- 3 egg yolks
- 2 cups all-purpose flour
- 1 teaspoon baking soda
- 1 teaspoon cream of tartar
- 1 pinch salt
- 1/2 teaspoon vanilla extract
- 1/4 cup white sugar, for rolling
- Preheat oven to 300 degrees F (150 degrees C).
- Beat 2 cups sugar, butter, and vegetable oil with an electric mixer in a large bowl until smooth. Add egg yolks one at a time, allowing each egg to blend into the butter mixture before adding the next. Sift flour, baking soda, cream of tartar, and salt into the egg yolk mixture; stir. Stir in vanilla extract. Roll the dough into walnut-sized balls.
- Spread 1/4 cup sugar onto a flat surface. Roll the balls of dough in sugar to coat. Arrange onto baking sheets spaced at least 2 inches apart.
- Bake in preheated oven cooked in the middle, but not yet browned, about 15 minutes.