Sweet Potato-Cauliflower Gratin with Crispy Sage Leaves

• 2 tablespoons extra-virgin olive oil
• 3 tablespoons all-purpose flour
• 1 cup whole milk
• 1/4 cup plus 1 tablespoon freshly grated Parmesan
• 20 fresh sage leaves, plus 1 tablespoon chopped fresh sage
• Coarse salt and freshly ground pepper
• 2 pounds sweet potatoes, peeled and sliced 1/4 inch thick
• 1 head cauliflower, quartered and sliced 1/4-inch thick
• Vegetable oil, for crisping sage

Preparation

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