Preheat the oven to 350°F (175°C).

Bring a large pot of water to a boil over high heat. Add the jumbo pasta shells and return to a boil. Cook the pasta uncovered until it’s just slightly firm to the bite, about 13 minutes. Drain well.

In a large skillet, brown the ground beef and drain any excess fat. Stir in the taco seasoning and water, then cook over low heat until the mixture thickens, about 5 minutes. Stir in the refried beans and ¾ cup of Cheddar cheese into the taco meat. Carefully spoon the meat mixture into the cooked pasta shells.

Spread ¼ cup of salsa over the bottom of a 9x13-inch baking dish. Arrange the stuffed shells over the salsa. Pour the remaining salsa over the shells.

Bake in the preheated oven for 40 minutes. Remove from the oven and sprinkle with sliced green onions and ¼ cup of shredded Cheddar cheese. Serve with sour cream if desired.