Ingredient:

• 8 medium Yukon Gold potatoes, peeled
• 3 medium sweet potatoes, peeled
• 2 tablespoons canola oil
• 1/2 teaspoon salt
• 1/4 teaspoon pepper
• 1/4 cup butter
• 3 garlic cloves, minced
• 1 tablespoon minced fresh thyme or 1 teaspoon dried thyme
• 1/2 cup shredded cheddar cheese
• 1/3 cup grated Parmesan cheese
• Additional minced fresh thyme, optional