CHEESY ROOT VEGETABLE GRATIN - High Desert Farmers Market

Ingredients

• 1 tbsp unsalted butter softened
• 12 long sweet potatoes (about 2 inches thick), peeled
• 34 large parsnips, ends trimmed and peeled
• 35 small beets, peeled
• 14 tbsp heavy cream, divided (whole milk is fine, but mixture won't thicken as much or be as creamy)
• 4 oz grated Parmesan, divided
• 1 tbsp fresh minced thyme, divided plus more for garnish
• 1 garlic clove, minced
• 1 oz shredded gruyere
• salt and pepper to taste