Sift together flour and cocoa powder; set aside. Use a mixer to blend together the butter and granulated sugar. Add vanilla, salt, and egg to mixing bowl and beat until blended. Pour the flour/cocoa mixture directly into the mixing bowl. Mix until dough is well combined.
In the palm of your hand, roll into ball one inch in diameter. Bake 10 minutes on parchment paper-lined cookie sheet. Cool on racks and then sift confectionery sugar on top.
Recipe by 2 Sisters 2 Cities at https://www.2sisters2cities.com/2012/12/six-chocolate-velvet-butter-balls/