Brown the ground beef, onion, and garlic in a large skillet until no pink is left.
Mix in the hot water, tomato paste, beef bouillon, and oregano. Simmer uncovered for 30 minutes until reduced to your desired consistency.
Mix the cottage cheese, beaten egg, grated parmesan, and one cup of shredded mozzarella in a small bow.
Preheat the oven to 350 F. Stuff the cooked pasta shells with the cheese and egg mixture and arrange them in a greased 9x13-inch casserole dish.
Spoon the meat sauce over the pasta shells, cover with foil, and bake for 30 mins. Remove the foil, sprinkle with the rest of the mozzarella cheese, and bake for five more minutes until the cheese is melted.