Uneven Lemon Mousse Results

A reader has asked: I have a great recipe for lemon mousse, but sometimes it has a bitter taste. I can’t figure out what I’m doing wrong sometimes but not others.

A: If your mousse has grated lemon zest in it you have to be careful just to grate off the yellow part of the rind and none of the bitter pith underneath—this may be the root of your problem.