Sweet Potato-Cauliflower Gratin with Crispy Sage Leaves

INGREDIENTS

2 tbsp

extra-virgin olive oil

3 tbsp

all-purpose flour

1 cup

whole milk

1/4 cup

plus 1 tablespoon freshly grated Parmesan

fresh sage leaves, plus 1 tablespoon chopped fresh sage

Coarse salt and freshly ground pepper

2 lb

sweet potatoes, peeled and sliced 1/4 inch thick

head cauliflower, quartered and sliced 1/4-inch thick

Vegetable oil, for crisping sage