Chop the pistachios very finely. Cut marshmallows in half. Peel bananas and cut them in half lengthwise. Melt butter in a pan. Fry the banana halves in it in portions while turning for about 3 minutes. Take out and distribute on plates.
Spread the marshmallows on the bananas and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 5 minutes until the marshmallows are golden brown. Arrange ice cream on top, garnish with pistachios and chocolate sauce.
Serve immediately.