Heat oven to 350° F (177° C). Line a small baking sheet with parchment paper or a silicone baking mat.
Using an electric hand mixer, cream the butter and sugar together until light and fluffy. This process should take about 1 minute for the best texture.
Add the egg yolk and vanilla to the mixture, blending well to ensure a uniform consistency.
Gently mix in the flour, ensuring it’s fully incorporated into the batter.
Scoop the dough into 1 ½ tablespoon-sized portions and place them on a cookie sheet. Roll each portion into a smooth ball.
Press a hole into the center of each ball, using your thumb or a 1 teaspoon measuring spoon for uniformity.
Spoon about 1/2 teaspoon of jam into each thumbprint.
Place the cookies in the oven and bake for 8 to 10 minutes, until they’re perfectly set and lightly golden.Pro Tip: Consider sprinkling powdered sugar over the baked thumbprint cookies. This adds a delightful touch, particularly when presenting these cookies as part of a holiday food gift.
Notes
Read the Recipe First: Take a moment to read through the full recipe and ingredient notes before starting. These cookies come together quickly, so it’s helpful to have all your ingredients prepped and ready to go.
Optional Sugar Coating: For added sweetness and texture, you can roll the cookie dough balls in granulated sugar before baking. This step is entirely optional, based on your preference.
Measure Flour Correctly: Spoon the flour into a dry measuring cup and level it off with the back of a knife. Avoid scooping directly from the bag, as it packs the flour too tightly and can affect the texture of your cookies.
Use Room Temperature Jam: Soft, room temperature jam is easier to spoon into the cookies and won’t stiffen the dough.