Authentic German Rouladen

Name: Authentic German Rouladen
Prep time: 25 min
Cook time: 1 h 30 min
Total time: 1 h 55 min
Cuisine: German
Ingredients: 1 ½ pounds flank steak or beef top round; 8 slices bacon; 8 tsp Dijon mustard; 8 whole gherkins, cut in half lenghtwise; 4 TBSP onion slices; 3-5 TBSP heat-resistant oil such as avocado, lard, or tallow; 1 large carrot; 2-3 stalks celery; 1 small leek; 1 cup red wine; 1 ⅓ cups bouillon or stock; 1 whole bay leaf; 1-2 TBSP butter; 1-2 TBSP AP flour; 2-3 TBSP tomato paste; salt & pepper to taste