Combine the peppercorns, thyme, bay leaves, cloves, garlic, and whole juniper berries in a small mixing bowl and set aside. Combine the water, sugar, and salt in a saucepan over medium-high heat. Bring to a boil and stir to dissolve the sugar and salt. Remove from the heat and add the dry spice mixture. Steep for 1 hour.
Place the duck breast pieces in a glass or plastic container. Pour in the seasoned brine to cover the breasts completely. Cover and refrigerate for 48 hours, turning the duck 2 to 3 times.
Remove the duck breasts from the brine and rinse thoroughly with cool water. Pat dry with a towel.
Preheat the oven to 250ºF.
Combine the crushed juniper berries and ground black pepper in a small bowl. Using the palm and heel of your hands, press two thirds of the berry and pepper mixture into the underside of the breasts. Press the remaining mixture onto the skin side. Place the breasts, skin side down, on a rack in a roasting pan and bake for 1 hour. Remove and let cool for 30 minutes.
Wrap the breasts tightly in plastic wrap and place in an airtight container. Store in the refrigerator for at least 1 week before using.
To serve, remove the meat from the bones and slice thin.
Yield: 6 servings