Melt the butter in a large heavy bottomed pot and add the rutabagas, shallots and leeks. Saute them on low to medium heat for about 10 minutes.
Then add in the cider, cover and simmer on low until the rutabagas are tender. This could take 30 minutes, give or take. Add a little extra water if the pot runs dry before the rutabaga are tender.
Transfer to the bowl of a processor along with the cream and process till smooth. Season well with salt and pepper and set aside. You can make this ahead and reheat on the stove or in the microwave.
Drizzle some olive oil in a baking dish and put the cod fillets in. Sprinkle liberally with salt and bake at 375 for about 20 minutes, and then pop them under the broiler for a minute or two to get brown.
https://theviewfromgreatisland.com/cod-over-rutabaga-puree/ September 19, 2011