Poach the Peaches: Place the bourbon, water and granulated sugar in a large, deep, straight sided skillet and stir to combine. Add the peaches, skin side down, to the pan. Bring contents to a simmer over medium high heat. Reduce heat to maintain a simmer and poach for 10-12 minutes.
Remove peaches with a slotted spoon to a clean work surface (leaving the bourbon water in the pan!). When cool enough to handle peel and slice peaches. Place slices on a large sheet of wax paper and transfer to the freezer. Freeze until firm.
Meanwhile: Continue to simmer the bourbon for 10-12 minutes or until reduced by about half. Transfer to a container, cover, and set in the refrigerator. Allow to cool completely.
For the Sorbet: In a blender or bowl of a food processor place sugar, ginger, lemon juice, and a heaping ½ cup of the reduced bourbon water. Blitz or pulse until combined. Add in the peach slices and blend or process until creamy and smooth. Transfer to a loaf pan and freeze, for at least 6 hours, or up to 1 week.
For the Mascarpone: Place mascarpone and bourbon in the bowl of a stand mixer or a small bowl. Use the whisk attachment, or a hand held mixer, to whisk mascarpone with bourbon until light and airy. Set aside in the refrigerator until ready to use.
Serve**: Serve heaping scoops of the peach sorbet topped with a dollop of whipped mascarpone and sprinkled with chopped pistachios and zested lemon.
*Yield: 1 Quart *Inactive Time of 6+ Hours *Can substitute frozen peaches, defrosted *Let the Frozen Sorbet sit at room temperature for 10 minutes before serving.