The Best Chocolate Espresso Thumbprint Cookies

Directions

• In a large bowl, cream together the softened butter, granulated sugar, and brown sugar with an electric mixer until light and fluffy, about 2-3 minutes.
• Beat in the egg yolk and vanilla extract until well combined.
• In a separate medium bowl, whisk together the flour, cocoa powder, instant espresso powder, baking soda, and salt.
• Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
• Cover the dough and chill for at least 30 minutes, or up to 2 hours. This helps prevent spreading.
• Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
• Roll the chilled dough into 1-inch balls and place them about 2 inches apart on the prepared baking sheets.
• Using your thumb or the back of a small round measuring spoon, create an indentation in the center of each cookie ball.
• Bake for 10-12 minutes, or until the edges are set and slightly firm. The centers may still look soft. If the indentations puff up, gently press them down again with your thumb or spoon immediately after removing from the oven.
• Let cookies cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.
• For the Ganache: Place the chopped chocolate in a heatproof bowl. Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer. Pour the hot cream over the chocolate and let sit for 5 minutes.
• Whisk the ganache until smooth and glossy. Let it cool for about 10-15 minutes, stirring occasionally, until it thickens slightly but is still pourable.
• Spoon or pipe the cooled ganache into the indentations of the cooled cookies. Allow the ganache to set at room temperature or in the refrigerator before serving.