Preheat oven to 400°F (200°C).

Heat oil in a roasting pan over medium-high heat.

Sear the stewing steak in the hot oil until browned on all sides.

Add diced bacon, onions, and halved mushrooms to the pan.

Sauté the bacon, onions, and mushrooms for 4-5 minutes, or until the onions are translucent.

Season the mixture to taste with salt and pepper.

Add the crumbled pumpernickel bread to the pan and stir to combine.

Pour in the dark beer and beef bouillon.

Bring the mixture to a boil, then cover the roasting pan with a lid or foil.

Transfer the pan to the preheated oven and cook for approximately 1 1/2 hours, or until the meat is tender.

About 5 minutes before the end of the cooking time, remove the pan from the oven and stir in the sliced gherkins and drained pickled onions.

Serve the goulash hot, sprinkled with freshly ground black pepper and a dollop of sour cream.