1. Preheat oven to 350°F (175°C) and line a 9×13 inch baking pan with parchment paper, leaving overhang.

2. In a large bowl, whisk together melted butter and sugar until well combined.

3. Add eggs one at a time, whisking after each addition, then stir in vanilla extract.

4. In a medium bowl, whisk together cocoa powder, flour, baking powder, and salt.

5. Gradually fold dry ingredients into wet mixture with a rubber spatula until just combined.

6. Fold in chocolate chips if using.

7. Pour batter into prepared pan and spread evenly.

8. Bake for 25–30 minutes, or until a toothpick inserted comes out with moist crumbs.

9. Let brownies cool in the pan on a wire rack for 30 minutes.

10. Use parchment overhang to lift brownies out and cool completely on rack for 1–2 hours.

11. Optionally chill brownies in the fridge for 30 minutes for cleaner cuts.

12. Press a heart-shaped cookie cutter firmly into cooled brownies and lift out.

13. Repeat cutting across the slab; save the scraps for snacking.

14. Dip cookie cutter in hot water and wipe dry between cuts for sharp edges.

15. Optionally decorate with powdered sugar, melted chocolate, or festive sprinkles.