Combine the duck meat, egg, sage, salt, pepper, nutmeg, and brandy in a mixing bowl. Set aside.

Place the duck breast skin-side down on a work surface and flatten it with a meat pounder. Butterfly each side of the breast and pond the meat to make it an even thickness to cover the entire skin surface. Try to shape it into a rectangle.

Arrange several layers of prosciutto, covering the entire surfaces of the breast. Place half of the ground mixture, lengthwise, all the way down the center of the breast to form a line about 1 inch wide. Arrange the fruit and pistachios in a pattern in the center of the ground mixture. Cover with the remaining ground meat.

Roll the breast into a cylinder, completely encasing the ground mixture. Wrap the galantine tightly in cheesecloth and tie the ends to secure. To maintain the shape, tie the galantine every 2 to 3 inches along the length with kitchen string.

In a pot large enough to hold the galantine, heat the olive oil over medium-high heat and brown the breast on all sides. Add the stock and wine, bring to a boil, lower to a simmer, and poach the galantine for 30 to 40 minutes, depending on the size, turning often. Remove from the broth and let cool. Refrigerate overnight before serving,

To serve, remove cheesecloth and cut 1/4-inch-thick slices and arrange them in overlapping rows on a tray.