Columbia River Root Vegetable Gratin
Serving Size:4-6|Prep Time:20minutes|Cook Time:1hour

  1. Preheat oven to 425ºF. Use a shallow 2-quart ceramic or glass casserole dish for even baking and easy cleanup.
  2. Cream ¼ cup of the butter with the ground mustard seed and the grated mustard or horseradish root. Coat the bottom and sides of the baking dish with the mustard flavored butter.
  3. Combine the potatoes and celery root in a bowl and place the mixed roots in the prepared baking dish. Level the sliced roots evenly over the bottom and press down slightly.
  4. In a bowl, beat the egg yolks and whole eggs with a fork to blend thoroughly.
  5. Add the heavy cream, salt, and pepper to the eggs and mix well. Pour the custard over the sliced roots.
  6. Dot the top of the casserole with the remaining 2 tablespoons of butter. Bake in the middle of the oven for approximately 30 minutes or until golden brown.
  7. Turn the oven down to 350°F, remove the casserole from the oven and loosely cover with foil. Return the casserole to the oven and bake another 20-30 minutes or until the vegetables are tender when pierced with a knife tip and the knife comes away clean indicating the custard is set.
  8. Let the finished casserole stand for 10-15 minutes before serving. This allows the flavors to ripen and firms the ingredients making it easy to dish up.
Chef’s Narrative
With a small salad of tender greens tossed with nut oil, champagne vinegar and toasted nuts, this gratin makes a satisfying luncheon meal. For dinner, serve it with your favorite grilled, poached or steamed white fish, or with roast turkey or standing rib roast.
Recipe Substitutions
Substitutions (optional) Try substituting sweet potatoes and grated onions for a completely different casserole that is a wonderful accompaniment for roast turkey, chicken, or goose. If you don’t have fresh celery root, substitute sunchokes and 2 tablespoons of minced celery.
  • ¼ cupplus 2 tablespoons unsalted butter – room temperature
  • ½teaspoondry mustard seed powder
  • 4ouncesmustard root or horseradish root – peeled and finely grated, (should yield about 3 – 4 tablespoons of grated root)
  • 4, about 1 ½- 2 pounds, medium-size starchy potatoes, peeled and sliced thinly, about 6 cups – russets work well here
  • ½poundcelery root – peeled and sliced thinly, about 4 cups
  • 2egg yolks
  • 2 whole eggs
  • 2cups heavy cream
  • 1 ½ teaspoonssalt
  • ¼teaspoonfreshly ground pepper

AllergensMilk, Eggs