Place butter and chocolate in a heat-proof bowl and microwave in 20 or 30-second increments, stirring between each, until melted. Alternatively, melt butter and chocolate over a double boiler. Do not overheat.

In a medium bowl, combine flour, ground almonds, baking powder, and salt.

In the bowl of an electric mixer fitted with the whisk attachment, whisk eggs and sugar on high speed until fluffy and foamy and pale yellow. Reduce speed to medium or medium-high and slowly add the chocolate mixture, then the vanilla extract and liquor. Add the flour mixture and mix just until combined. The batter will be too runny at this point, so place it in the fridge for 60 minutes or longer until it firms up.

Place powdered sugar a small bowl.

Using a teaspoon or an ice-cream scoop (I used this one), scoop 1 inch/2.5 cm rounded pieces of dough, and roll them into balls between your hands. Roll each ball generously in powdered sugar, and place on prepared baking sheets, spacing them 2 inches apart.

Bake for 8-10 minutes, until cookies are cracked and still soft in the center. Overbaking the cookies will make them dry. Allow cookies to cool on the baking sheets for 10 minutes, then transfer them to a wire rack to cool completely.

Cookies can be stored in an airtight container at room temperature for 3 days.