Step 1Heat the oven to 350 degrees. Grease a 3-quart baking dish.
Step 2Melt 6 tablespoons of butter in a large skillet over medium-low heat. Add the onions and cook until very tender, 10 minutes. Add the mushrooms and sprinkle with salt and pepper to taste, the paprika and a dash of cayenne. Cook until the mushrooms are tender and the onions are browned, 10 minutes. If liquid remains in the pan, cook over high heat, stirring, a few minutes until it evaporates. (If you don't have a large enough skillet, you can divide the ingredients among 2 skillets.)
Step 3Cook the noodles uncovered in a large pot of boiling salted water over high heat until they're nearly tender but firmer than usual, 5 minutes. Drain, rinse them with cold water and drain well. Transfer them to a large bowl. Add the mushroom mixture and mix well. Add the cottage cheese and sour cream; mix well. Taste, and season the mixture generously. Stir in the eggs.
Step 4Pour the noodle mixture into the dish. Dot the top with the remaining 2 tablespoons of butter and sprinkle lightly with paprika. Bake the kugel uncovered until set and lightly browned on top, 1 hour. Serve from the baking dish.