Preheat your oven to 350°F (175°C) and prepare a 9x13-inch baking pan with nonstick cooking spray and parchment paper.

Melt the unsalted butter in a medium saucepan over low-medium heat, then remove from heat and let cool slightly.

Whisk the granulated sugar and light brown sugar into the melted butter, followed by the vanilla extract.

Incorporate the eggs one at a time, whisking well after each addition.

In a separate bowl, mix the flour, cocoa powder, salt, and baking powder together until combined.

Gradually fold in the dry ingredients into the wet mixture until just combined, then fold in the chocolate chips and nuts if using.

Pour the batter into the prepared pan and smooth the top before baking for 22-28 minutes.

Once baked, cool the brownies in the pan for at least 1 to 1.5 hours before chilling in the refrigerator.

Lift the slab out using the parchment overhang and cut into heart shapes with cookie cutters.

Dust with powdered sugar or drizzle with melted chocolate before serving.