• Preheat the oven to 375°F. Line two large baking trays with silicone mats or parchment paper.

Preparing the Cookie Dough:

• Place all the softened butter into a large mixing bowl. Add the white and light brown sugars. Using a mixer, cream the butter and sugar together, beating for 5 to 6 minutes, until the butter is fluffy and creamy.
• Next, add in the vanilla extract, eggs, and salt. Mix again for a few minutes until the eggs are well incorporated.
• Add the first 2 cups of flour to the batter and beat with the mixer. If you’re using a stand mixer, you can continue to add the remaining flour gradually, mixing on low speed. Otherwise, switch to a wooden spoon and gradually work in the remaining flour. The dough will look dry and crumbly at first but keep mixing until it’s smooth. I like to use my hands to bring the dough together.
• Use a small cookie scoop (about 1 ½ tablespoons, or 25 grams) to measure out the dough for each cookie. Gently roll each scoop into a neat dough ball and place onto a tray.

Adding the Filling:

• You can make all the cookies one flavor or try several different fillings. If adding chopped nuts, place them into a small bowl, then firmly roll each cookie dough ball in the nuts. Use your hands to roll each dough ball back into shape.
• Place the cookie dough balls onto the prepared baking sheets. Space the cookies apart about 1 ½-inches; they will not spread.
• Use the back of a ½-teaspoon measuring spoon or the end of a round wooden rod and press down over the center of each dough ball, creating a deep well for the filling.
• Drop approximately 1 teaspoon of jam into the center of each cookie.   

Baking, Serving, & Storing:

• Bake the cookies at 375°F for 12 to 14 minutes, just until the bottom of the cookies turns a light golden brown. Allow the cookies to cool on the baking sheet for a few minutes before transferring over to a wire cooling rack to cool.
• The jam filling inside these thumbprint cookies will get super-hot while baking! Allow the cookies to cool down before enjoying them.
• Enjoy these thumbprint cookies with coffee, tea, or hot chocolate. Store the cookies at room temperature in an air-tight container for up to 1 week. For longer storage, place the cookies into a freezer-friendly container and freeze for up to 4 months.