Port-And-Spice Poached Pears With Granita

Peel pears, leaving stems intact. Cut a round of parchment paper to fit inside a wide 4-quart heavy pot.
Bring grape juice, Port, sugar, spices, and 1 cup water to a boil in pot over moderate heat, stirring until sugar is dissolved. Add pears, arranging them on their sides in 1 layer (pears will not be covered by liquid). Cover pears directly with round of parchment. Reduce heat to low and poach pears, turning occasionally, until just tender when pierced with a sharp knife, about 25 minutes. Remove from heat and let pears steep in liquid, covered with parchment, turning occasionally, at least 2 hours and up to 3.
Carefully transfer pears with a slotted spoon to a shallow dish, reserving poaching liquid. Let pears stand at room temperature or chill, covered with parchment.
Pour poaching liquid through a fine-mesh sieve into a bowl (discard spices) and return to pot. Boil, uncovered, until liquid is reduced to about 2 1/2 cups, 25 to 30 minutes. Remove from heat and stir in lemon juice and remaining 1/4 cup water. Pour liquid into an 8- to 9-inch square baking pan (not nonstick).
Freeze liquid 1 1/2 hours, then scrape and stir with a fork, crushing any lumps. Repeat, scraping every hour until evenly frozen, about 4 hours more.
Bring chilled pears to room temperature before serving, about 30 minutes.
Cut a thin slice from bottom of each pear, then stand pears upright on chilled plates. Scrape granita, then serve pears with granita and creme fraiche.