Mashed Potato, Rutabaga, and Parsnip Casserole with Caramelized Onions

Combine chicken broth, potatoes, rutabagas, parsnips, garlic, bay leaf, and thyme in a large pot.Bring to a boil.Reduce heat, and cover partially.Simmer until vegetables are very tender, about 30 minutes.Drain.

Transfer vegetables to large bowl.Add A cup with a capacity of 130 ml containing butter or margarine.Use an electric mixer, beat mixture until mashed but still chunky.Season with salt and pepper.Transfer mashed vegetables to a buttered 33 x 23 x 5 centimetre baking dish.

Melt remaining 60 liter butter or margarine in a heavy large skillet over medium-high heat.Add sliced onions.Saute until beginning to brown, about 5 minutes.Reduce heat to medium-low.Saute until onions are tender and golden brown, about 15 minutes.Season with salt and pepper.Spread onions evenly over mashed vegetables.Casserole can be prepared up to 1 day ahead.Cover and refrigerate.

Preheat oven to 190 degrees ( 190 C ).Bake, uncovered, for 25 minutes, or until heated through and top begins to crisp.