In a pot of salted boiling water, cook spaghetti until just shy of al dente (about 1 minute less than the package directs). Reserve pasta cooking water.
Meanwhile, in a large skillet, combine 6 tablespoons oil and garlic. Add pinch of red pepper flakes, if using. Cook over medium heat until garlic is very lightly golden, about 5 minutes. (Adjust heat as necessary to keep it gently sizzling.)
Transfer pasta to skillet along with 1/2 cup pasta water, increase heat to high, and cook, stirring and tossing rapidly, until a creamy, emulsified sauce forms and coats the noodles. Remove from heat, add remaining 2 tablespoons olive oil, and stir well to combine. Mix in parsley, if using, and serve right away.
Preheat oven to 350 degrees F (175 degrees C). Bring a large pot of lightly salted water to a boil, add pasta, and cook until done; drain.
In 9×13 inch baking dish, stir together macaroni, shredded Cheddar cheese, cottage cheese, sour cream, Parmesan cheese, salt and pepper. In a small bowl, mix together bread crumbs and melted butter. Sprinkle topping over macaroni mixture.