Preheat the oven to 350 F. In a medium bowl, whisk together flour, cocoa powder, salt, and baking soda. In a large bowl, combine butter with sugar until fluffy.
Add in egg and vanilla extract, and mix until smooth. Add in the flour mixture, and mix until it is fully combined. Add in the green food coloring, and mix until it is fully green.
Use a cookie scoop to place the cookies onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes. Remove from the oven and place a chocolate kiss on each cookie.
