Time: not long, I'd say
Mum sent me this one from Australia. No idea who invented it; but it is so, so, so yummy, and so, so, so easy.
Preheat oven to 180°C.
Mix all the raw stuff together well.
Press the mixture into a shallow tin and bake [for how long?].
While hot, spread chocolate icing all over, and cut into slices when it is warm.
Quick and easy. You could throw in a few chopped walnuts or hazelnuts.