Step 1: Preheat the Oven

1. Set the Temperature: Preheat your oven to 350°F (175°C).

Step 2: Prepare the Baking Pan

1. Grease the Pan: Lightly grease an 8×8-inch (20x20cm) baking pan with butter or cooking spray.
2. Line with Parchment Paper: For easy removal, line the pan with parchment paper, leaving an overhang on the sides.

Step 3: Mix the Dry Ingredients

1. Combine Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.

Step 4: Mix the Wet Ingredients

1. Beat the Eggs: In a large mixing bowl, whisk the eggs until frothy.
2. Add Sugars: Add the granulated sugar and brown sugar, mixing until well combined.
3. Incorporate Greek Yogurt: Stir in the Greek yogurt and vanilla extract until smooth.

Step 5: Combine Wet and Dry Ingredients

1. Fold in Dry Ingredients: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Avoid overmixing to prevent dense brownies.
2. Add Chocolate Chips: Gently fold in the dark chocolate chips (and optional add-ins like nuts or espresso powder).

Step 6: Bake the Brownies

1. Transfer to Pan: Pour the batter into the prepared baking pan, spreading it evenly with a spatula.
2. Bake: Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (but not wet batter).

Step 7: Cool and Serve

1. Cool in Pan: Let the brownies cool in the pan for 10-15 minutes.
2. Remove and Slice: Use the parchment paper overhang to lift the brownies out of the pan. Transfer them to a wire rack to cool completely before slicing.