Creating delicious Chocolate Thumbprint Cookies is as easy as following this step-by-step guide:

1. Preheat the Oven: Begin by preheating your oven to 350°F (175°C). Line a baking sheet with parchment paper.
2. Cream Butter and Sugar: In a large mixing bowl, cream together the softened butter and granulated sugar until smooth and fluffy.
3. Add Egg Yolk and Vanilla: Mix in the egg yolk and vanilla extract until thoroughly combined.
4. Combine Dry Ingredients: In another bowl, sift together the all-purpose flour, cocoa powder, and salt. Gradually add this mixture to the wet ingredients, stirring until a dough forms.
5. Shape Cookies: Roll the dough into balls, about 1 inch in diameter, and place them on the prepared baking sheet.
6. Create Thumbprints: Use your thumb (or a small round object) to make an indentation in the center of each ball.
7. Fill with Chocolate or Jams: Place a small amount of chocolate chips or your chosen filling in the center of each thumbprint.
8. Bake: Place the baking sheet in the preheated oven and bake for 10-12 minutes, or until the edges set.
9. Cool: Remove the cookies from the oven and allow them to cool on the baking sheet for about 5 minutes. Then, transfer them to a wire rack to cool completely.
10. Dust with Powdered Sugar: If desired, dust with powdered sugar before serving.

By following these steps, you’ll be well on your way to creating mouthwatering Chocolate Thumbprint Cookies that everyone will love!