We all underwent it: Great festival, merchandising booths bought blank, but now hungry and no money at all anymore ...
Good being prepared and have been baking at home Festival-Lembas and brought them along:

Take: half bag of muesli, nuts and almonds as much as you can get. Roast it altogether with a sizably dab of butter in a big pan.
Let it cool off. Not until it´s really cool, put into: 1 little bag vanilla suggar, 2 eggs, 1 teaspoon baking soda and a generous amount of sugar or honey (at least 1 cup of it).
Cover a baking tin with baking parchment. Now just put the mix of muesli in drops or - for tough fellows - completely onto the baking parchment. In the baking oven at 175 degrees about 10 minutes to bake. That´s it.

Don´t forget to bring along to the next festival!