Preheat oven to 350 degrees. Coat a 9” baking dish with cooking spay and set aside.
Cook shells in a large pot of boiling water, stirring often and cook until just tender, according to package directions. Drain and rinse under cold water. Set aside.
In the meantime, in a blender, add ½ slice bread, including crust. Grind into crumbs. Set aside.
Heat oil in a large nonstick skillet over medium heat. Add onions, garlic and cook, stirring often, until onions are soft. Stir in thawed spinach and mix well. Set aside.
In a medium bowl, combine cottage cheese, bread crumbs and 2 tablespoons Parmesan cheese. Mix well. Stir in cooked onions and spinach. Stir in the egg white. Season with Italian seasonings and fresh ground pepper, to taste.
Stuff each of the cooked shells with a generous 2 tablespoons of the cottage cheese mixture. Spread ½ cup pasta sauce in the bottom of a 9” baking dish. Arrange stuffed shells in a single layer, 3 rows of 5 shells. Top shells with remaining 1 cup sauce and sprinkle with the remaining 1½ tablespoons Parmesan cheese. Bake for 30 minutes, until the top is golden and the shells are heated through. Let cool for 10 minutes before serving.