Whisk together sugar, cocoa powder, and evaporated milk in a sauce pan and heat on stovetop. Stirring constantly, bring to a boil for 3 min. Remove from heat and stir in butter and vanilla.
Place one brownie square in dish and top with 3 scoops of ice cream.
Slice 1 banana lengthwise and place on sides of ice cream.
Place a second brownie square on top of ice cream.
Drizzle with hot fudge sauce. Top with whipped cream and a maraschino cherry. Sprinkle with nuts if desired.