Preheat oven to 350 degrees.
Lightly coat a mini muffin tin with vegetable shortening.
In a large bowl, whisk together the flour, cocoa powder, salt and baking soda.
In another large bowl, beat the sugar and butter together for 1-2 minutes.
Add the egg and vanilla extract and beat until combined.
Slowly add the dry ingredients into the wet ingredients and beat until combined.
Add about 1 tsp of cookie dough to each mini muffin cavity. (¾ full)
Bake cookie cups for 10-12 minutes.
Cookie cups will be soft when they come out of the oven. Use the back of a measuring spoon, shot glass or other small circle to gently press in the center of each cookie cup.
Allow the cookies to rest for 5 minutes before removing them to a wire cooling rack.
Allow the cookies to cool completely before adding the icing.