1. Preheat your oven. Position your oven rack to the center and preheat to 350°F (175°C). Proper oven temperature is essential for even baking and achieving that perfect fudgy texture.
2. Prepare your baking pan. Line an 8×8 or 9×9 inch baking pan with parchment paper, allowing the paper to overhang the sides slightly. This makes brownie removal and cutting much easier. Alternatively, lightly coat the pan with cooking spray or butter.
3. Melt chocolate and butter. Place ½ cup butter and 4 ounces chopped chocolate in a medium saucepan over medium-low heat. Stir frequently as they melt, about 3-4 minutes. The mixture should be smooth and well combined. Remove from heat and let cool for about 2 minutes.
4. Whisk in cocoa powder. Add ¾ cup unsweetened cocoa powder to the melted chocolate mixture and whisk vigorously, breaking up any lumps. This ensures smooth texture and prevents grittiness. The mixture will be thick and glossy—this is perfect.
5. Add sugars. Stir in 1 cup granulated sugar and ½ cup packed brown sugar. Mix thoroughly until well combined. The sugars will partially dissolve as you stir, and the mixture will look thick and fudgy.
6. Incorporate eggs. Add 2 room-temperature eggs one at a time, stirring well after each addition. Room-temperature eggs incorporate more smoothly than cold eggs. The mixture will become glossy and smooth.
7. Add vanilla. Stir in 1 teaspoon vanilla extract, mixing until well combined.
8. Combine dry ingredients separately. In a separate bowl, whisk together ¾ cup all-purpose flour, ¼ teaspoon baking powder, and ½ teaspoon salt. Whisking combines these ingredients evenly and helps incorporate air.
9. Fold in dry ingredients. Add the flour mixture to the wet ingredients and fold gently with a rubber spatula until just combined. Don’t overmix—overmixing develops gluten, which can make brownies cake-like instead of fudgy. Fold until no dry flour streaks remain.
10. Add nuts (optional). If desired, fold in ½ cup crushed walnuts or pecans. These add crunch and sophistication to every bite.
11. Pour into prepared pan. Transfer the batter to your prepared baking pan, spreading it evenly. Use an offset spatula or the back of a spoon to create an even layer.
12. Bake until set. Bake for 25-30 minutes. Brownies are done when a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter, but a few fudgy crumbs). Don’t overbake—overbaking creates dry brownies. A little underbaking is better than overbaking for fudgy brownies.
13. Cool in pan. Remove brownies from the oven and let them cool in the pan for about 10-15 minutes. They’ll continue cooking slightly during this cooling time, and the cooling process helps them set properly.
14. Cut into squares. Using a sharp knife, cut the cooled brownies into 9-12 squares depending on desired size. For more generous sundaes, cut larger squares. Wipe your knife between cuts for cleaner edges.

For Assembling the Sundae:

15. Warm your brownies gently. If brownie sundaes will be served later, you can warm individual brownie squares in the oven at 300°F (150°C) for about 2-3 minutes just before serving, or microwave for 10-15 seconds. Warm brownies create that wonderful temperature contrast with cold ice cream.
16. Place brownie in serving bowl. Position one warm brownie square in the center of your serving bowl or plate.
17. Add ice cream scoops. Place 2 generous scoops of vanilla ice cream on top of or next to the brownie. The warm brownie will partially melt the ice cream, creating wonderful texture contrast.
18. Drizzle with hot fudge. Pour approximately 3 tablespoons of hot fudge sauce over the ice cream and brownie, allowing it to cascade down the sides. Make it generous and artistic!
19. Top with whipped cream. Add a generous dollop of whipped cream on top, using a spoon to create attractive peaks and swirls.
20. Add festive toppings. Sprinkle with crushed nuts, colorful sprinkles, or your favorite toppings. Crown with a maraschino cherry if desired. Place a wafer cookie standing at an angle if you want extra elegance.
21. Serve immediately. Brownie sundaes are best enjoyed right away while the brownie is still warm and the ice cream is still cold. This temperature contrast is what makes them special.