Potato and Celeriac Gratin - Edible Santa Barbara and Wine Country

Ingredients

• 4 ounces crème fraîche
• 3/4 cup cream
• Salt and pepper
• 1 pound potatoes (russets or Yukon Golds), peeled and very thinly sliced on a mandoline)
• 1 pound celeriac ((celery root), peeled, very thinly sliced on a mandoline)
• 2 tablespoons chives (finely chopped)
• 3 green onions (finely sliced)
• 2 ounces Gruyère cheese (grated)