Preheat oven to 425°F – (be sure oven rack is in the middle position) Cook noodles in a large pot of boiling salted water making sure they are truly ‘al dente’, since they’re going to cook more in the dish.

Melt butter in a large heavy skillet over moderate heat and brush muffin cups with some of butter. Add onions to skillet and cook, stirring occasionally, until nicely browned, probably about 20 minutes. Transfer onions into a large bowl and stir in noodles, sour cream, cottage cheese, and (poppy seeds if desired). Lightly beat eggs with salt and pepper, then stir into noodle mixture until combined well.

Divide mixture among muffin cups and bake until puffed and golden, 20 to 25 minutes. Loosen edges of kugels with a thin knife and cool kugels in pan 5 minutes before serving.