01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper.
02 - In a bowl, whisk melted butter with sugar until combined. Add eggs and vanilla, whisking until smooth.
03 - Sift together flour, cocoa powder, and salt. Fold into the wet mixture gently until just combined.
04 - Pour batter into the prepared pan, smooth the surface, and bake for 25 to 30 minutes until a toothpick inserted in the center comes out with moist crumbs. Cool completely, then cut into 6 squares.
05 - Combine heavy cream, chopped chocolate, butter, and sugar in a saucepan over medium heat. Stir continuously until smooth and melted, about 3 to 4 minutes. Remove from heat and stir in vanilla and a pinch of salt.
06 - Place a brownie square in a dessert bowl. Top with a scoop of vanilla ice cream. Drizzle hot fudge sauce over the top. Garnish with whipped cream, nuts, and a cherry if desired. Serve immediately.