Susan ran across my bag of muddy roots in the fridge and suggested that it was time to do something with them. Even with the excessive trimming that the deer and I had inflicted before putting them in storage, the roots came out of two months of refrigeration in good shape. I lined a milk crate with a black trash bag and scooped some soil-less planter medium (peat moss and vermiculite) into the bag. The roots were packed together, and more medium spread around them so that the roots were well supported. I watered the mix slightly, so that a handful of medium would pack, but no water would squeeze out.
The witloof (Belgian endive) requires warm temperatures to start budding, and needs to be kept out of light to stay blanched. I tied off the black plastic bag to make a light-proof tent, and put it in our furnace room to stay warm. The bag will need to be opened every few days to circulate the air and prevent mustiness. We should have some chicons ready in 20 days or so.