3 guy and gratin Recipes

parsnips, peeled, sweet potato, peeled, celery root, peeled, russet potatoes, peeled, heavy cream, low-sodium chicken stock, dried tarragon, minced garlic, gorgonzola cheese, crumbled, salt, freshly ground black pepper, special equipment : a 1 1/4 quart oval gratin dish

white mushroom, unsalted butter, plus more for buttering the dish, salt, spinach, stemmed, washed and drained (about 2 bunches), heavy cream, fresh ground black pepper, sea salt