Preheat your oven to 350°F (180°C) and line an 8x8-inch baking pan with parchment paper.

Chop the dark baking chocolate into small pieces, then melt in the microwave in 20-30 second bursts until smooth. Let cool slightly.

Mix the Greek yogurt and sweetener into the cooled chocolate mixture until creamy and uniform.

In a separate bowl, whisk together the all-purpose flour, cocoa powder, and baking soda until evenly combined.

Gradually add the dry ingredient mixture to the chocolate mixture, stirring until just combined.

Add the milk and stir until the batter is smooth and consistent.

Fold in the chocolate chips if using, ensuring they are evenly distributed.

Pour the batter into the prepared baking pan and smooth the top.

Bake for 25-30 minutes until a toothpick inserted comes out clean or with a few moist crumbs.

Let the brownies cool in the pan for about 10 minutes before transferring to a wire rack to cool completely.