Today I am supposed to make a chocolate mousse for dinner and I need butter (melted).The shops are closed. Can I use vegetable oil instead of melted butter?
I would say no for two main reasons, the butter will change texture as the dessert cools, and I don't think the oil will, so the mousse will split. Also the tastes will be off.
You could try margarine, or at a real push lard (you would need to play around with the sugars to keep the sweetness)
However I have seen recipies that exclude butter, here is a link to one possibility.