Step 1: Preheat and Prepare the Baking Dish

Preheat your oven to 350°F (175°C). Lightly grease a 9×9-inch baking pan and line it with parchment paper for easy removal.

Step 2: Mix the Dry Ingredients

In a large bowl, whisk together the mochiko flour, cocoa powder, baking powder, and salt until well combined. This helps evenly distribute the dry ingredients, ensuring a smooth batter.

Step 3: Melt the Butter and Chocolate

In a microwave-safe bowl, melt the butter and dark chocolate together in 30-second intervals, stirring in between. Once melted, let it cool slightly before adding to the batter.

Step 4: Combine the Wet Ingredients

In another bowl, whisk together the granulated sugar, brown sugar, eggs, vanilla extract, and milk until smooth. Slowly pour in the melted butter and chocolate mixture, whisking continuously.

Step 5: Incorporate Dry and Wet Mixtures

Gradually fold the dry ingredients into the wet mixture, stirring until a thick, smooth batter forms. If using add-ins like chocolate chips or nuts, gently fold them in now.

Step 6: Bake the Brownies

Pour the batter into the prepared baking dish, spreading it evenly. Bake for 40–45 minutes, or until the top is set and slightly cracked. A toothpick inserted should come out with a few moist crumbs (not wet batter).

Step 7: Cool and Slice

Allow the brownies to cool completely in the pan before slicing. This ensures they set properly and maintain their chewy texture. For best results, chill in the refrigerator for 30 minutes before cutting.