I have been making this recipe for years. It is based on a recipe in the Dean and DeLuca cookbook by David Rosengarten. I have always found it to be a lovely holiday side dish. It goes well with prime rib roasts and roast chicken. It is versatile and can be made ahead to be put into the oven when needed and also is easily doubled. —thirschfeld
6 to 8
russet potatoes, peeled and cut into 1/2 inch chunks
celery root, peeled and cut into 1/2 inch chunks
If you plan to cook the gratin right away heat the oven to 400 degrees. Otherwise move on to step two.
Place the potatoes and celery root into separate large pots. Cover by two inches with cold water and add a teaspoon of salt to each pot. Bring the pots to a boil over medium heat. Cook the vegetables until tender.
Once the vegetables are tender, pour them out into a colander set in the sink. Drain the vegetables and let them sit for a minute or two steam-drying.
Rinse out one of the pots and add the cream, garlic, butter, and saffron. Bring the cream to a boil over medium heat. Add a hefty pinch of salt and a few grinds of white pepper. Add 1/2 cup of the cheese. Stir it into the warm liquid till melted.
Place the celery root and potatoes into a mixing bowl (or the other blanching pot if it is big enough) and smash the mix with a potato masher. Add a pinch of salt then add the cream and saffron mix. Stir to combine. Taste and adjust the seasoning, adding more salt or pepper if necessary.
Use a little softened butter to grease an 8-inch oval gratin (12 inches long). Spread the rustic chunky mash out into the pan. Smooth the top with a spatula, then crosshatch the top with the tines of a fork. Spread the remaining cheese out over the top.
Bake until the cheese is browned, about 30 minutes. Let the gratin cool for 5 minutes, then serve.