Peel the bananas, cut in half lengthways, place in a greased baking dish and drizzle with the lemon juice.
Roughly chop the marshmallows and sprinkle over the bananas.
Sprinkle the hazelnut kernels over the marshmallows and bake in the preheated oven at 160 degrees on the bottom rack for 10 minutes on top and bottom heat.
Let stand in the switched-off oven for another 3 minutes. The marshmallows must be melted.
Divide the bananas on 4 dessert bowls.
Add 2 scoops of vanilla ice cream at a time and drizzle with the chocolate sauce.