For most people, making a gingerbread house at the holidays is challenge enough. But Roz Cummins wanted to take it a step further this year: she decided to build an eco-house. What's the best way to make an edible green roof, which candy melts into the best solar panels, and what do red wiggler worms have to do with it all? Find out in a holiday column the likes of which you've never sampled before.