Sweet Potato and Pinto Bean Enchiladas

Name: Sweet Potato and Pinto Bean Enchiladas
Ingredients: 3 orange-fleshed sweet potatoes, peeled and cut into 1/2-inch (12-mm) dice; 2 Tbs. olive oil; Salt and freshly ground pepper, to taste; 12 tomatillos, husked, rinsed and halved; 4 poblano chilies, halved and seeded; 3 garlic cloves, unpeeled; 1 small white onion, chopped; 1 1/2 cups (1 1/2 oz./45 g) fresh cilantro leaves; 2 cans (each 14 oz./440 g) pinto beans, drained and rinsed; 10 large white corn tortillas; 3/4 cup (3 oz./90 g) shredded Monterey jack cheese; 2 avocados, halved, pitted, peeled and sliced (optional)