Root Vegetable Gratin

Preheat the oven to 350 degrees. Butter a 10 x 13 baking dish.

Heat 2 tbl of olive oil in a large saute pan over medium heat, add the onion and fennel, and cook for 10 minutes, tossing occcasionally, until lightly browned and tender. Add the garlic and cook for one minute.

Meanwhile, in a large bowl, combine the onion mixture, sweet potatoes, celery root, gold potatoes, cream, chicken stock, Gruyere, thyme, 1 tbl salt and 1 ¹⁄₂ tsp pepper. Pour the mixture into the prepared baking dish and press lightly so the vegetables lie flat all the way to the edge. Combine the bread crumbs and 2 tbl of olive oil and distribute evenly on top. Bake uncovered for 1 ¹⁄₂ hours until the vegetables are very tender when tested with a small knife and the top is browned and bubbly. Allow to set for 15 minutes and serve hot.