Special equipment: A wide saucepot, parchment paper, a parisienne scoop/small melon baller, a piping bag
Juice the lemon and orange, reserving the juiced citrus halves. Put the juice, citrus halves, wine, water, honey, ginger, black peppercorns, cloves, cardamom, star anise and bay leaf in a wide saucepot. Gently place the pears into the liquid. Make a circle of parchment paper that is 1/2-inch larger than the pot and cover surface completely with the parchment paper (see Cook's Note*). Make sure the pears are fully submerged but not touching the bottom of the pot. Bring the poaching liquid and pears to a boil, then reduce the heat to just below a simmer.
Cook the pears until fork tender. Test for doneness by inserting a sharp knife in the base; there should be little resistance when fully cooked. Gently transfer pears to a glass or ceramic bowl. Pour enough poaching liquid over pears just to cover. Cover and refrigerate for several hours, preferably overnight; the longer the pears soak, the darker they will become.
Strain remaining poaching liquid and return to saucepan. Cook over high heat until a syrupy consistency is achieved or the syrup coats the back of a spoon. Chill until the pears are served.
Use a parisienne scoop to remove each pear's core, hollowing out a 1-inch wide cavity that starts at the base and extends 3/4 of the way up the pear. Transfer the Creamy Pistachio Nut Filling to a piping bag without a tip. Gently fill the pear cavity until it slightly overflows. (The overflow will help to provide a sticky surface to stand the pear up on.) Place the pear, base side down, in a bowl and surround with 1-ounce of the syrup. Serve.
In a medium-sized bowl, cream the mascarpone, sugar, and vanilla together. Stir in the pistachio nuts.
Use immediately or refrigerate and return to room temperature before filling the pears.
Make sure the poaching liquid is kept below a simmer so that the delicate pears don't fall apart from the agitation of the liquid.