In a medium bowl, beat butter and sugars with a mixer at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add egg and vanilla bean paste, beating until combined. In a medium bowl, whisk together flour, cocoa, salt, and baking powder. Gradually add flour mixture to butter mixture, beating until combined.
Divide dough in half, and shape into 2 disks; wrap in plastic wrap. Refrigerate for at least 2 hours or overnight.
Preheat oven to 350°F. Line 2 baking sheets with parchment paper.
Roll each disk of dough between two sheets of parchment paper to ¼-inch thickness. Using a 2½-inch round cutter, cut dough, rerolling scraps as necessary. Place on prepared pans. Using a wooden pick, make decorative indentations in tops of cookies if desired.
Bake until slightly puffed, about 7 minutes. Let cool completely on wire racks.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/chocolate-cookies/