Banana cake with walnut toffee topping

Ingredients

• Banana cake
• 125 gram butter
• 3/4 cup sugar
• 2 eggs
• 2 ripe bananas, mashed
• 1 teaspoon baking soda
• 2 tablespoon milk
• 2 cup plain flour
• 1 teaspoon baking powder
• whipped cream, to serve
• Walnut toffee topping
• 1 firm banana, chopped
• 1/4 cup walnut pieces
• 50 gram butter, melted and mixed with 3 tbsp brown sugar