Apple and Celery Root Gratin with Gruyère - SippitySup

Ingredients

• 1 teaspoon unsalted butter
• 1 pound tart, crisp apples (pelled, halved and cored)
• 1 pound celery root (peeled and halved or quartered, depending on size)
• 1 cup heavy cream
• 1 teaspoon kosher salt (plus more for seasoning)
• ½ teaspoon grated nutmeg
• 1 pinch ground cloves
• 2 cups grated Gruyère cheese
• 1 cup roughly chopped, toasted walnuts
• 1 cup fresh breadcrumbs
• 1 tablespoon brown sugar