Combine all of the ingredients, including reserved duck fat, in a food processor, fitted with a metal blade. Process until the mixture if thoroughly mixed, but do not puree. Set aside. Using a sharp knife, cut a 4-inch slit across the top of pita. Stuff each pita with about 1/4 cup of the rillette, some of the julienne pears and a couple slices of the cheese.
Preheat the oven to 350ºF.
Place the pitas on a baking sheet. Bake for a couple of minutes, just until the cheese melts.
Remove from the oven and serve warm.
Yield: 8 sandwiches