Preheat the oven to 180C/350F. Line an 8 x 8-inch pan with parchment paper, and set aside.
In a microwave-safe bowl, add your chopped chocolate. Melt your chocolate. Let sit for 1-2 minutes, before adding your yogurt and sugar. Whisk until smooth and transfer to a large mixing bowl.
Add the flour, cocoa powder, and baking soda, and mix until just combined. Add your milk and mix well, until fully incorporated. Fold through your chocolate chips, if using them.
Transfer to the lined pan and bake the brownies for 25-30 minutes, or until a skewer comes out just clean. Remove from the oven and let cool in the pan for 10 minutes, before carefully transferring to a wire rack to cool completely.
* I used vanilla coconut Greek yogurt. Any non-fat or reduced fat yogurt works. TO STORE: Yogurt brownies will keep well at room temperature, in a sealed container. Be sure to lay a sheet of paper towel on top, to keep them super moist and fudgy. They will keep well for up to 5 days. To keep them longer, store them in the refrigerator. TO FREEZE: Brownies are freezer friendly and can be stored in the freezer for up to 6 months. Thaw overnight in the refrigerator or at room temperature.