Rinse the beef roulades and pat dry. Season both sides with salt and pepper. Brush each with 1 teaspoon of mustard, then place 1 slice of ham on top. Slice the pickles and peel the cooked eggs. Arrange pickle slices and 1 egg on each roulade, roll up tightly, and secure with toothpicks.
Peel and dice the onions. Peel and mince the garlic cloves. Clean and wash the leek, then cut into thin rings.
Heat the clarified butter in a deep pan over medium-high heat. Add the roulades and brown on all sides for 8 minutes. Add the onions, garlic, leek, and tomato paste, stirring well. Sprinkle the flour over the mixture and stir to combine. Pour in the red wine and stock, bring to a simmer, cover, and cook for 80 minutes.
Remove the roulades from the pan and keep warm. Strain the cooking liquid through a sieve and season to taste with salt and pepper.
Arrange the roulades on serving plates, pour the strained sauce over top, and serve with mashed potatoes or pasta.