Preheat oven to 350 degrees. Place several large spoonfuls of enchilada sauce on the bottom of a baking dish (enough to just cover the bottom). Set aside.

Cook ground beef with chopped green onions in large skillet on medium heat. When meat is cooked, drain and discard grease. Add taco seasoning packet and cook according to seasoning package instructions. Once meat has finished cooking, transfer it to a bowl, and let cool down for 4-5 minutes. Discard grease from pan. Add 3 Tablespoons enchilada sauce and HALF of the grated cheddar and jack cheeses to the meat; stir to combine. Set aside.

In a large pot of boiling salted water, cook jumbo pasta shells according to package directions. When pasta is done cooking, drain, then place shells in a single layer on wax paper or parchment paper. Fill cooked pasta shells with the ground beef mixture, then place into baking dish (on top of sauce) in a single layer.

Once all shells are filled and in baking dish, spoon the rest of the enchilada sauce over shells to cover. Sprinkle with the remaining half of the cheddar and jack cheeses.

Cover dish with aluminum foil and bake in preheated 350 degree oven for 25-30 minutes total. Remove foil for the last 10 minutes of baking. Sauce and cheese should be bubbly when done. Remove dish from oven.

To serve, garnish with additional cheese, chopped tomato, chopped cilantro, and green onions, for a great splash of color and flavor! Place 2-3 shells onto each person's plate; top each shell with a small dollop of sour cream. Serve and enjoy!