FOR THE RASPBERRY CURD
FOR THE COOKIES
TO MAKE COOKIES: In a medium-size bowl,using an electric mixer on medium speed, beat the butter until fluffy, about 1 minute. Add the brown sugar and beat for another minute. Next, add the egg yolk and vanilla and beat until well combined.
In a separate bowl, whisk together the cocoa powder, flour, baking soda, and salt until no lumps remain. Add the dry ingredients to the wet ingredients in two increments, mixing between each addition. Cover the dough and chill it for at least 1 hour. The dough can be made in advance or even frozen.
When ready to bake, preheat the oven to 350°F. Line a cookie sheet with parchment paper. (You can use cooking spray, alternatively).
Place the granulated sugar in a shallow bowl.
Scoop eight equal-size portions of dough, roll them in your hand to form perfect balls, and then roll through the sugar to coat. Space evenly apart on the prepared cookie sheet.
Bake for 8 to 10 minutes, until set in the center and beginning to crackle.
Let cool completely on the cookie sheet.
TO MAKE THE Raspberry CURD: in a medium-size sauce pan, melt the butter over medium heat. Add the raspberries, lemon juice, sugar, and salt. Bring to a simmer over medium-high heat, stirring occasionally. There should be tiny bubbles along the edges of the pan.
Place the egg yolks in a small bowl on the side. Add a small scoop of the simmering raspberry mixture to the egg yolks and stir vigorously. Repeat a few times Then, pour the entire egg yolk mixture back into the saucepan, and bring to a brisk simmer over medium-high heat, stirring occasionally. Cook for 1 minute, then remove from the heat and stir in the vanilla. Pour the raspberry mixture into a bowl, press plastic wrap directly on the surface, and refrigerate for at least 4 hours.
To serve, scoop the raspberry curd onto four of the cookies. Top with the remaining four cookies to make messy, delicious sandwiches
