Preheat the oven to 350°F and lightly spray a 12-cup muffin pan with cooking spray.
Cook the 8 oz spaghetti according to package directions until al dente, then drain well in a colander.
Transfer the drained spaghetti to a large bowl, toss with the 1/3 cup melted butter, then stir in the 2 whisked eggs and 1/2 cup grated Parmesan until the pasta is evenly coated.
Divide the coated spaghetti evenly among the 12 muffin cups and press the pasta down and up the sides to form little nests.
While the pasta cooks, brown the 1 lb Italian sausage in a skillet over medium heat, breaking it up as it cooks; drain excess fat.
Stir the 2 cups spaghetti sauce into the cooked sausage and remove from heat.
In a small bowl, mix the 3/4 cup cottage cheese with 1/4 cup Parmesan and 1 Tbsp dried parsley.
Spoon the cottage-cheese mixture evenly over each spaghetti nest in the muffin pan.
Top each cup with a portion of the sausage and sauce mixture, then sprinkle shredded mozzarella evenly over the tops.
Bake for 30 minutes, or until the cheese is melted and lightly browned; let cool a few minutes before removing from the pan.