For the rhubarb crumble, peel the rhubarb stalks (remove the skin) and cut into pieces. Melt the butter in a saucepan, add the rhubarb and stir briefly. Stir in honey and vanilla sugar and steam the rhubarb covered until firm to the bite, but not too soft. If necessary, add a little sugar and a dash of rum to taste.
Finely chop the pine or pistachio nuts, mix in and remove from the heat.
Preheat the oven to 180 °C. Grease a suitable ovenproof dish with melted butter and pour in the rhubarb.
For the crumble, put all the ingredients in a bowl and mix with your hands until crumbly. Spread over the rhubarb and bake the rhubarb crumble in the hot oven for about 25 minutes until golden.