In planning for this dish, take care to choose sweetbreads that are white, plump, and firm. They spoil quickly and should be prepared within twenty-four hours of purchase.
One 1 1/2 pound veal sweetbread lobe 1 tablespoon plus 1 teaspoon black peppercorns 4 bay leaves 1 cup champagne or sparkling wine Juice from 1 lemon (2 tablespoons) 1 tablespoon chopped shallots 1 tablespoon chopped garlic 1 pound salted butter, cut into pieces 3 tablespoons nonpareil capers, drained 1 tablespoon salt 1/2 tablespoon freshly ground white pepper 1/2 tablespoon freshly ground black pepper 1 cup all purpose flour 1 cup clarified butter
Place the sweetbread in a medium saucepan with 1 teaspoon of the peppercorns and the bay leaves.
Add enough cold water to fully submerge the sweetbread.
Bring to a boil over high heat, then lower heat to medium-high and cook for 5 minutes. The desired doneness is medium. The blanched sweetbread will be firm but will still give to the touch.
Drain and set aside to cool.
To make the beurre blanc, set a small saucepan over medium heat. Add the champagne, lemon juice, the remaining 1 tablespoon peppercorns, the shallots, and garlic.
Simmer for 5 minutes, or until reduced by one-third.
Whisking constantly, add the salted butter to the liquid one piece at a time until it has all been incorporated into the sauce.
Remove from the heat and strain through a fine-mesh strainer into a fresh saucepan. Discard the solids.
Add the capers to the strained sauce and set aside while you prepare the sweetbread.
When the sweetbread has cooled, use a small, sharp knife to remove the outer membrane. The sweetbread will be very fragile. Take extreme care as you cut it into twelve 1/4 inch-thick medallions.
Season them with the salt and black and white pepper and carefully dust with the flour. In a large sauté pan, heat the clarified butter over medium-high heat. The butter is hot enough when a small pinch of flour sizzles in the pan.
Using a spatula, gently add the sweetbreads to the pan and sauté for 3 1/2 minutes per side, until golden brown. Remove to a plate lined with paper towels to drain.
Divide the sautéed sweetbread medallions among 6 appetizer plates.
Nap the beurre blanc across the center of the medallions, allowing some sauce to pool on the plate. The dish is most attractive when the capers are clustered at the centers of the medallions.