Preheat the oven to 350°F (175°C) and lightly spray a 12-cup muffin pan with cooking spray.
Cook the 8 oz spaghetti according to package directions until al dente; drain in a colander and return to a mixing bowl.
Stir the 1/3 cup melted butter into the hot pasta, then add the 2 whisked eggs and 1/2 cup grated Parmesan; toss until the spaghetti is evenly coated.
Divide the spaghetti mixture evenly among the 12 muffin cups and press down to form nests or cups.
While the pasta cooks, brown 1 lb ground beef or turkey in a 10-inch skillet, breaking it up with a masher or spatula; drain any excess fat.
Add the 1-oz taco seasoning, the 10 oz can diced tomatoes with green chiles (undrained), and 1/4 cup water to the browned meat; simmer about 5 minutes.
Remove the skillet from heat and stir in 2 cups spaghetti sauce; set the meat sauce aside.
In a small bowl, combine 3/4 cup cottage cheese, 1/4 cup Parmesan, and 1 tbsp dried parsley; spoon this cheese mixture evenly into each spaghetti cup.
Spoon the meat and sauce mixture over each cottage-cheese–filled spaghetti cup (you may have some sauce left over).
Top each cup with shredded cheddar or Mexican cheese blend, then bake for 30 minutes, until the cheese is lightly browned.
Let the pies cool briefly in the pan, then remove and serve with any leftover sauce if desired.