Ingredients

• 1 cup all purpose flour
• 1/3 cup unsweetened cocoa powder
• 1/4 teaspoon salt
• 1/2 cup (1 stick) unsalted butter, softened
• 2/3 cup granulated sugar
• 1 egg (separated into 1 egg white and 1 egg yolk)
• 2 tablespoons milk
• 1 teaspoon vanilla extract
• 1/2 cup ground pistachios
• 2 ounces semisweet chocolate, chopped
• 2 tablespoons heavy whipping cream
• 2 tablespoons Irish cream

Instructions

1. In a large bowl, thoroughly whisk together the all-purpose flour, unsweetened cocoa powder, and salt until well combined. Set aside.
2. In a separate large mixing bowl, beat the softened unsalted butter and granulated sugar together using an electric mixer until the mixture is light, fluffy, and creamy, typically 2-3 minutes. Incorporate the egg yolk, milk, and vanilla extract, beating until just combined. Gradually add the dry flour mixture to the wet ingredients, mixing on low speed until a cohesive dough forms. Do not overmix. Gather the dough, flatten it into a disk, wrap it tightly in plastic wrap, and chill in the refrigerator for at least 2 hours, or preferably overnight. This step is crucial for preventing the cookies from spreading.
3. Once the dough is adequately chilled, preheat your oven to 350°F (175°C). Line three cookie sheets* with parchment paper or lightly grease them to prevent sticking.
4. Prepare your coating stations: In one small shallow bowl, lightly whisk the egg white until slightly frothy. In a second shallow bowl, add the finely ground pistachios.
5. Using a 1-inch cookie scoop (or about 1 tablespoon of dough), scoop the dough into uniform balls. Roll each dough ball first into the whisked egg white, ensuring it’s lightly coated, then immediately roll it into the ground pistachios, pressing gently to ensure an even coating. Place the coated dough ball on the prepared cookie sheet, about 1 inch apart. Using your thumb or the back of a rounded teaspoon, gently make an indent into the center of each cookie, being careful not to flatten the cookie too much or press all the way through the bottom.
6. Bake for 10 minutes, or until the edges of the cookies are set and firm. Keep a close eye on them to prevent overbaking, as chocolate cookies can be difficult to tell when done. If the indentations have puffed up during baking, gently use the back of a teaspoon to re-indent the centers while the cookies are still warm and pliable. Allow the cookies to cool on the baking tray for 3 minutes before carefully transferring them to a wire rack to cool completely. This ensures they firm up and don’t break.
7. Once the cookies are entirely cooled, it’s time to prepare the luxurious Irish cream ganache filling: Place the finely chopped semisweet chocolate into a heatproof bowl. Set this aside.
8. In a small saucepan, combine the heavy whipping cream and Irish cream. Heat this mixture over medium heat until it is steaming hot around the edges, but do not allow it to come to a rolling boil. Remove the saucepan from the heat and immediately pour the hot cream mixture over the chopped chocolate in the heatproof bowl. Let it sit undisturbed for 1 minute to allow the chocolate to melt. After 1 minute, whisk the mixture gently from the center outwards until everything is smooth, glossy, and fully emulsified. If, for any reason, the cream mixture wasn’t hot enough and the chocolate hasn’t fully melted, you can gently reheat the ganache in the microwave in 10-second intervals (stirring between each) or return it to a saucepan over very low heat, stirring constantly until smooth.
9. Using a small spoon or a piping bag, carefully spoon or pipe some of the warm ganache into the center of each thumbprint**. Fill them generously but ensure the ganache doesn’t spill over the edges. Allow the chocolate ganache to fully set and harden at room temperature for at least 30-60 minutes before serving. For a quicker set, you can refrigerate them briefly.

Notes