Mixed Root Vegetable Gratin

• butter for the pan
• 2 medium parsnips, peeled and thinly sliced
• 1 large baking potato, peeled and thinly sliced
• 1/2 small celery root, pared and thinly sliced
• 1¾ cups heavy cream, plus more as needed
• 2/3 cup whole milk
• 1 garlic clove, crushed
• pinch of nutmeg
• salt and freshly ground black pepper
• ½ cup shredded Gruyére cheese

1. Preheat the oven to 350°F (180°C). Butter the gratin dish; Overlapping the slices, layer the parsnips, potato, and the celery root.

2. Mix the cream, milk, garlic, and nutmeg, season with salt and pepper. Pour over vegetables. Sprinkle with the cheese. Bake for 1 hour, or until tender and golden. Let stand 5 minutes then serve hot.