Preheat the oven to 400 degrees F.

Grind whole peppercorns in a spice grinder or with a mortar and pestle until course. Brush 2 tablespoons of the mustard on the steaks, and season on each side with 1/2 teaspoon of the salt and ground peppercorns.

Heat a large skillet until very hot. Add some oil and sear steaks until well browned and crisp on 1 side, about 3 minutes. Flip steaks and put the skillet in oven for about 5 minutes, for medium-rare. Remove steaks from the oven. Place steaks on a dish and cover with aluminum foil to keep warm.

Place the skillet over medium heat. Add the shallots and cook until soft, about 2 minutes. Season with salt and pepper. Add the green peppercorns, then the wine and cook until the liquid has reduced by half. Whisk in the veal stock and cream and bring to a simmer. Spoon the sauce over the steaks and serve immediately with the Frites.

Place the potato slices in a bowl of water. Let stand 15 minutes. Drain, rinse under cold water, and drain again. Pat dry with towels.

Heat enough oil to come 4 inches up the sides of a large deep saucepan to 350 degrees F. Add the potatoes in batches and cook until just crisp but still yellow, about 5 minutes. Remove from the pan with a slotted spoon and drain on paper towels. Sprinkle with salt and herbs and serve immediately.