Serves 4
4 medium sweet potatoes (8 to 10 ounces each), pricked all over with a fork
2 tablespoons olive oil
2 garlic cloves, thinly sliced crosswise
1 bunch kale (about 1 1/4 pounds), thick stems removed, leaves torn into large pieces and washed with water left clinging
Coarse salt and ground pepper
1 to 2 tablespoons balsamic vinegar
1/2 teaspoon red-pepper flakes
1 cup part-skim ricotta cheese