01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper.
02 - Melt butter and semisweet chocolate chips in a heatproof bowl over simmering water, stirring until smooth. Remove from heat.
03 - Whisk in granulated sugar, then add eggs one at a time, followed by vanilla extract.
04 - Fold in all-purpose flour and salt gently until just combined. Avoid overmixing.
05 - Pour batter into prepared pan and smooth surface. Bake 25 to 30 minutes until a toothpick inserted in the center comes out with moist crumbs. Let cool completely, then cut into six squares.
06 - Combine heavy cream, semisweet chocolate chips, butter, and corn syrup in a saucepan over medium heat. Stir until melted and smooth. Remove from heat and stir in vanilla extract and a pinch of salt.
07 - Place one brownie square in each serving bowl. Top with a generous scoop of vanilla ice cream, drizzle hot fudge sauce over it, then add whipped cream, nuts if desired, and finish with a maraschino cherry.