Cream butter, yogurt and sugar together until very creamy.
Add egg and mint extract and beat until pale and smooth, about 2-3 minutes.
Combine flour with salt, baking powder, baking soda, and cocoa powder. Slowly mix into the wet ingredients. Stir in the chocolate chips gently.
Scoop about ½ tablespoon of batter onto cookie sheet, leaving 1 inch between brownie bites (I use a small cookie scoop.)
Bake for 6-8 minutes until batter is set. Cool slightly on tray and then cool completely on wire rack.
Once cookies are cooled, mix the powdered sugar with the water and a the tiniest drops of peppermint extract (VERY potent stuff) and drizzle over brownie bites while still on cooling rack. This step is not necessary but dresses up these little bites.