Trim and slice the Beef Top Round into thin cutlets (about 1/4 inch). Lightly season both sides with Salt and freshly ground Black Pepper. Spread a thin layer of Mustard over each cutlet.
Prepare the filling: chop the Bacon and cook in a skillet over medium heat until the fat renders and the bacon is crisp. Remove most of the fat, then add chopped Onion and grated or finely diced Carrot to the pan and sauté until soft and lightly golden. Stir in finely chopped Dill Pickles, cook 1 minute more, then transfer the filling to a bowl to cool slightly.
Place a spoonful of the bacon–vegetable mixture near one end of each beef cutlet and roll up tightly, tucking in the sides. Secure the rolls with kitchen twine or toothpicks.
Lightly dredge each roulade in All-Purpose Flour, shaking off any excess.
In a heavy skillet, heat a splash of Vegetable Oil and a knob of Butter over medium‑high heat. Brown the roulades on all sides until nicely caramelized, working in batches if needed. Transfer the browned roulades to a Dutch oven or deep pan.
Pour enough Beef Broth into the pan to come about halfway up the roulades. Add 1–2 Bay Leaves and a few whole Black Peppercorns. Bring to a gentle simmer, cover, and braise on low heat (or in a 325°F/160°C oven) for about 1 to 1 1/2 hours, until the beef is tender.
When the roulades are done, remove them from the cooking liquid and keep warm. Strain or skim the sauce if desired, then reduce it over medium heat to concentrate the flavor. Off the heat, stir in a few tablespoons of Sour Cream to enrich the sauce and adjust seasoning with additional Salt and Black Pepper to taste.
Return the roulades to the sauce to warm briefly, slice each roulade into rounds if you like, and spoon the creamy sauce over them. Serve hot with mashed potatoes or buttered noodles.
