Winter Vegetable Gratin

Ingredients

• 1 small onion, chopped
• 1 tablespoon butter
• 1 garlic clove, minced
• 1-1/2 cups heavy whipping cream
• 1/2 cup sour cream
• 4-1/2 teaspoons minced fresh rosemary or 1-1/2 teaspoons dried rosemary, crushed
• 1 tablespoon minced fresh basil or 1 teaspoon dried basil
• 1/2 teaspoon salt
• 1/2 teaspoon pepper
• 1/2 teaspoon ground cumin
• 3 medium Yukon Gold potatoes, peeled and thinly sliced
• 2 medium turnips, peeled and thinly sliced
• 1 medium sweet potato, peeled and thinly sliced