1. Heat the oven to 250°. Cover a baking sheet with paper towels. In a large heavy frying pan, heat 1 tablespoon of the oil over moderately high heat. Sprinkle the shrimp with the salt and pepper. Put the shrimp in the pan and cook, stirring, until just done, about 4 minutes. Remove the shrimp from the pan.
2. Lay the tortillas on a work surface. Cover half of each with the beans. Top with the cheese and then the shrimp. Fold the tortillas in half.
3. In the frying pan, heat the remaining 3 tablespoons oil over moderately high heat. Add four enchiladas and brown, about 30 seconds per side. Put on the baking sheet and keep warm in the oven. Repeat with the remaining enchiladas.
4. Drain the oil from the frying pan and then return four of the enchiladas to the pan. Put the rest in a second frying pan. Over moderate heat, add half the salsa to each pan and cook until the tortillas are slightly softened, turning once, about 2 minutes in all. Serve the enchiladas topped with dollops of sour cream and the chives.
Fish Alternatives: If available, crawfish tails, often sold already cooked, would be fantastic here. Or you can buy cooked shrimp to save yourself a step.
Wine Recommendation: Beer is always a safe bet with Mexican food. But think about trying a glass of cold rosé, such as a white zinfandel or the drier vin gris from California.