To make chocolate sauce: Place the chocolate and cream in a microwave-safe jug. Microwave, uncovered, on high for 2 to 3 minutes, stirring every minute with a metal spoon or until smooth. Stir in Kahlua, if desired.
Place banana slices into a wafer cone. Top with scoops of ice-cream.
Drizzle with chocolate sauce. Sprinkle with nuts. Serve.