1.Preheat oven to 350F (180C). In a large bowl, stir beans with sour cream, red peppers, onions, garlic, chipotle, paprika, cumin and salt. Then stir in 1 cup (250 mL) each coriander and cheese until evenly mixed. Lightly coat a 9x13-inch (3-L) baking dish with oil. Completely cover bottom with a single layer of tortillas. Try not to overlap too much. If necessary, use scissors to cut to fit.
2.Spread one-third of sour cream mixture over tortillas. Spoon 2/3 cup (150 mL) salsa overtop. Sprinkle with 1/2 cup (125 mL) coriander. Repeat layering 2 more times. Finish with 1 cup (250 mL) cheese.
3.Bake, uncovered, in centre of preheated oven until casserole is bubbly and cheese is melted, 35 to 40 minutes. Let stand 10 minutes before serving. Sprinkle with remaining 1/2 cup (125 mL) coriander. Best eaten the same day it's made, but leftovers will keep well, covered and refrigerated, overnight. Reheat in microwave on medium.