1. Preheat the oven to 350°. Drop the noodles into about 2 quarts of boiling salted water. Boil for 10 minutes, or until barely tender.
2. Strain them through a colander or strainer, rinse them thoroughly with cold water, then drain. Spread the noodles out on a board and cut them into pieces as long as they are wide, making squares of about 1 inch.
3. Melt half the butter in an 8-inch skillet. When the foam subsides, add the onions. Cook them for 4 or 5 minutes, or until they are translucent.
4. Add the noodle squares and the rest of the butter and toss them about until they are well coated. Cook over moderate heat for about 5 minutes.
5. With a wire whisk, beat the sour cream and eggs together in a large mixing bowl. Stir in the ham, a generous grinding of pepper, salt and the contents of the skillet.
6. Butter a 2-quart casserole, scatter the bread crumbs over the butter, tip the casserole from side to side to spread them evenly, then fill the casserole with the noodle-and-ham mixture. Bake, uncovered, in the middle of the oven for 45 minutes, or until the mixture is firm.
7. To unmold, run a sharp thin knife around the inside of the casserole, place a warm platter over the top of it and, grasping the casserole and the platter together, turn them over. Serve with the bottom side up.
8. "Schinkenfleckerln" is usually served for a light lunch or supper, preceded by soup and accompanied by a salad.
