"The base of this recipe came from our area, the German community of a small town in Delhi, Ontario Canada. I've tweaked it a bit over time. My family loves this, and it's a good way to spend a cold afternoon. I serve this with whipped potatoes and a vegetable - tonight we had beets in Harvard sauce."
Heat 1 tablespoon butter over medium heat in a large frying pan; stir in 1 onion and saute until softened, about 5 minutes. Set aside to cool slightly.
Stir pork, ground beef, bread crumbs, salt, and pepper together in a bowl; stir in onion. Pour beaten eggs over meat mixture; mix with your hands until well combined.
Spread about 1 1/2 tablespoons of meat mixture onto each beef slice; top each with one pickle quarter. Roll beef slices around filling; secure each roll with a toothpick.
Heat 2 tablespoons butter in the same frying pan; place rolls into pan and brown on all sides, about 10 minutes. Remove rolls; place in a single layer in a roasting pan.
Heat remaining 2 tablespoons butter in the same frying pan over medium heat; cook and stir remaining onion, celery, carrots, and garlic until vegetables are soft, about 10 minutes. Stir in 3 cups water, tomato paste, sherry, bouillon granules, and bay leaf; bring to a boil. Pour sauce over rolls in roasting pan.
Bake in the preheated oven until tender, about 3 hours; remove from oven to turn rolls over halfway through the cooking time.
Remove rolls to a heated platter. Place roasting pan with sauce on the stove; bring to a boil. Whisk cornstarch and 1/3 cup water together in a cup; slowly whisk cornstarch mixture into sauce until thickened, about 5 minutes. Drizzle some sauce over the rouladen; serve the remaining sauce in a gravy boat.