Preheat the oven to 350°F and lightly spray a 12-cup muffin pan with cooking spray.
Cook the spaghetti according to package directions until al dente, drain, and return to a bowl.
Toss the hot spaghetti with melted butter, then add the whisked eggs and 1/2 cup grated Parmesan; mix thoroughly so the pasta is evenly coated.
Divide the spaghetti evenly into the 12 muffin cups and press the pasta down and up the sides to form cups.
While the pasta cooks, brown the ground beef or turkey in a 10-inch skillet, breaking it up with a masher or spoon; drain excess fat.
Add the taco seasoning, the can of diced tomatoes with green chiles (undrained), and 1/4 cup water to the skillet; simmer for about 5 minutes.
Remove the skillet from heat and stir in 2 cups spaghetti sauce until combined; set the taco meat sauce aside.
In a small bowl, combine 3/4 cup cottage cheese, 1/4 cup Parmesan, and 1 tablespoon dried parsley; divide this cheese mixture evenly over each spaghetti cup.
Spoon the meat and sauce mixture over the cheese layer in each spaghetti cup (you may have some sauce left over).
Top each cup with shredded cheddar (or Mexican blend) and bake for 30 minutes, until the cheese is lightly browned.
Remove from the oven and let cool slightly before serving; serve with any leftover sauce if desired.
