In a small saucepan, combine the Bordeaux wine with whole black and white peppercorns. Over medium heat, bring the mixture to a gentle simmer, allowing it to reduce by half for about 10-15 minutes.

Melt unsalted butter in a separate skillet over medium heat. Add the finely chopped shallots and sauté them for about 3-4 minutes, stirring occasionally until they become translucent and fragrant.

Once the wine has reduced, strain it through a fine mesh sieve directly into the skillet with the sautéed shallots. Discard the peppercorns.

Stir in Dijon mustard and Worcestershire sauce into the shallot and wine mixture. Return to heat and let the sauce simmer for an additional 5 minutes, stirring occasionally.

Taste the sauce and season with salt as needed. Remove from heat when it reaches a velvety texture.

Serve the sauce generously over cooked steak and garnish with fresh chopped parsley.