1 cup fat (I used butter, vegan butter, vegetable shortening, and extra virgin coconut oil and all worked great)
1/4 cup granulated sugar
3/4 cup light brown sugar
2 large eggs
2 teaspoons vanilla extract
Heat oven to 350°F and arrange rack in the middle. Line a baking sheet with a Silpat or parchment paper.
Combine flour, baking soda, and salt in a medium bowl. Whisk to mix and break up any lumps.
Combine fat and sugars in the bowl of a stand mixer fitted with the paddle attachment. Beat until light and creamy, about 1-2 minutes.
Scrape down the sides of the bowl and add eggs one at a time, letting the first one incorporate completely before adding the second. Add vanilla and beat another minute.
Add flour and mix on low until fully incorporated. Add any mix-ins like chocolate chips, dried fruit, nuts, and mix on low until combined.
Scoop dough onto prepared baking sheet and space about 1-inch apart. Bake 10-12 minutes or until lightly browned on the edges but still soft in the middle. Let cool on the baking sheet about 5 minutes then remove to a wire rack to cool completely.
For Whole Wheat Thumbprints with Jam or Dulce de Leche:
Change flour amount to 1 cup all-purpose and 1 3/4 cups whole wheat flour. Chill dough for at least 1 hour then roll dough into balls and bake as directed above. When they come out of the oven, immediately press a indentation in the middle with a round wooden spoon handle. Fill each hole with a heaping 1/4 teaspoon of your favorite jam (I used strawberry) or dulce de leche.
For Sprinkle Cookies:
Add 1/2 cup sprinkles (I like nonpareils but jimmys also work) to the dough with the flour. Pour another 1/2 cup of sprinkles in a shallow dish. Chill dough for at least 1 hour. Roll into balls and then flatten slightly. Dip the top of each cookie into the sprinkles pressing gently to adhere. Bake as directed, adding more sprinkles right after they come out of the oven if you want them completely covered.
For Chocolate Sugar Cookies:
Add 3/4 cup unsweetened cocoa powder to the flour mixture. Roll dough into balls as directed then roll each ball in granulated sugar before baking. Bake as directed.