Begin by laying out your top round beef slices on a clean cutting board. Using a meat mallet, gently pound each slice to about ¼ inch thick. Season both sides generously with kosher salt and black pepper.

Spread a thin layer of yellow German mustard evenly across each beef slice. Next, layer the strips of bacon, dill pickles, and chopped onions on top. Carefully roll each slice tightly, securing with toothpicks.

In a large skillet, heat unsalted butter and olive oil over medium-high heat. Brown the rouladen for 3-4 minutes on each side, then remove from skillet.

In the same skillet, add chopped onions, carrot, celery, and minced garlic. Sauté over medium heat for 5-7 minutes until soft and fragrant.

Add soy sauce, beef broth, and tomato paste to the skillet. Stir to combine and let simmer for 2-3 minutes.

Reduce heat and add the browned rouladen back into the skillet. Cover and simmer gently for 1.5 to 2 hours.

Remove the rouladen and strain the broth. Return the liquid to the pot, bring to a simmer, and whisk in a slurry of cornstarch and water.

Stir in chilled butter into the thickened gravy. Adjust seasoning as needed and simmer for a few more minutes.

Serve each beef roulade on a platter, spoon thick gravy over top, and garnish with parsley. Enjoy!