Preheat oven to 325 F.
In a large bowl, using an electric mixer, cream together the sugar and butter for 5 minutes.
Add the egg yolk and beat.
Whisk together the baking powder, cocoa powder, and flour in a smaller bowl.
Add to the creamed sugar mixture and beat just until incorporated.
Wrap the dough and place it in the refrigerator to cool.
Next, place the pistachios in a food processor and grind them into small pieces.
Roll out the dough into 1-inch balls.
Make an imprint by pressing your thumb into each cookie.
Add the egg white into a small bowl and whisk.
Roll the edge of the cookie into the egg white.
Roll the edges of the cookie into the crushed pistachios.
Place on a parchment-lined baking sheet.
Repeat until all cookies are garnished.
Using a spoon, add a small amount of raspberry jam into the centre of each.
Bake for approximately 15 minutes.
Allow cookies to cool before transferring to a wire rack.
