Cook shells in boiling, salted water for 10 minutes or until al dente. Rinse under cold water to stop the cooking, drain on paper towels.
Combine cottage cheese, ¾ cup yogurt cheese, and all of the cheddar cheese in a large bowl. Mix in beaten egg. Add beef mixture to the bowl, stir to combine well. Spoon the filling into the pasta shells and arrange over the sauce. Sprinkle the remaining 1¼ cups yogurt cheese over the shells. Bake for 30 minutes or until the filling is thoroughly heated and the cheese is melted and bubbly.
Recipe by My Lilikoi Kitchen at https://www.mylilikoikitchen.com/2017/04/12/cheesy-beef-stuffed-shells/