This is a great side dish with a flexible recipe.  Use whatever proportions of rutabaga and carrots that you have on hand and it will come out good. 

2 lbs rutabaga, peeled and cut into 1 inch chunks
2 lbs carrots, peeled and cut into 1 inch chunks
3-6 TBLS butter, to taste
sugar, honey or other sweetener, to taste (optional)
salt and pepper to taste

In a large pot cover rutabaga and carrots with water.  Bring to a boil, reduce heat, and simmer until the vegetables are fork tender.  Drain well.  Mash by hand or use a food processor to puree.  Add butter, sweetener, salt and pepper to taste.

Store in a tightly lidded container in the fridge for a couple days and reheat to serve.