Add the dark chocolate and unsalted butter to a microwave-safe bowl.
Microwave on high for 30 seconds, then remove and stir well. Continue microwaving in 30-second intervals, stirring well between each interval, until the chocolate and butter are completely melted and smooth. Set aside to cool.
Add the eggs, white sugar, and brown sugar to a large mixing bowl.
Using an electric hand mixer, beat until the eggs becomes pale, thick, and doubles in volume. When you lift the whisk, the mixture should leave visible ribbons or trails on the surface that quickly disappear.
Pour the melted chocolate and butter mixture into the whipped eggs, and add the vanilla extract and gently mix until everything is well combined.
Sift in the flour and cocoa powder, then add a pinch of salt. Gently mix until just combined and there are no visible streaks of dry flour. Avoid overmixing.
Line a 22 × 17 × 4.5 cm baking pan with parchment paper.
Pour the brownie batter into the pan and gently tap the pan for a few times to release any large air bubbles.
Bake at 170°C (338°F) for about 15 minutes.
Let the brownies cool completely to room temperature.
Once cooled, refrigerate for at least 4 hours, preferably overnight. Chilling the brownies makes them much easier to cut and insert onto sticks without falling apart.
Place the semi-sweet chocolate in a deep, microwave-safe glass.
Microwave in short intervals, stirring well between each interval, until completely melted and smooth.
Remove the chilled brownie from the pan and cut it into 8 equal squares.
Insert 2 wooden skewers or popsicle sticks into each brownie so that they look like popsicles.
Dip each brownie into the melted chocolate, making sure it is completely covered.
The coating will be thick, so allow the excess chocolate to drip off. If needed, gently run the brownie against the edge of the glass to remove some of the excess chocolate.
Place each chocolate-coated brownie onto a baking sheet lined with parchment paper.
While the chocolate is still wet, decorate with your Halloween-themed sprinkles. Have fun with this part, you can make each brownie look different!
Place the decorated brownie pops in the refrigerator until the chocolate coating is completely set.
Once set, they’re ready to serve!