Preheat oven to 350 degrees F. Line the inside of a 9 inch round springform pan with nonstick foil.

In a large saucepan or in a microwave-safe bowl, melt the 4 tablespoons of butter over medium heat. Stir in the sugar and cocoa powder. Let cool slightly, then whisk in the egg, yolk, salt, vanilla and buttermilk. Stir in the flour. Pour into the pan and bake for about 18 minutes or until set. Let cool completely and keep chilled until ready to use.

Soften the mint ice cream. When ice cream is soft, spread it as evenly as possible across the brownie layer. Put a sheet of plastic wrap over it and freeze for an hour or until firm. When firm, soften the chocolate ice cream and spread chocolate ice cream over the mint ice cream.

When both layers of ice cream are very firm, pipe or spread whipped cream over the top. Store in freezer until ready to serve. Before serving, remove springform and peel away the foil. Drizzle with chocolate syrup if desired.