How to Make It
In a pot just large enough to hold the pork, combine the cream with the buttermilk, butter, garlic, cheese rind and 1 sage sprig. Season the pork with salt and pepper and add to the pot. Bring just to a simmer. Cover, leaving it open just a crack, and cook over low heat for about 3 1/2 hours, until very tender. Transfer the pork and garlic to a large plate; discard the cheese rind.
Boil the poaching liquid over moderately high heat, whisking occasionally, until thickened, about 20 minutes. Strain the sauce into a bowl. Whisk in the lemon juice and season with salt and pepper; keep warm.
Meanwhile, preheat the oven to 450°. On a large baking sheet, toss the fennel and the remaining sage sprig with the olive oil and season with salt and pepper. Arrange the fennel in a single layer. Place the pork on top of the fennel and roast until the pork is deeply golden and the fennel is tender, about 20 minutes. Transfer the pork to a cutting board and let rest for 15 minutes.
Thinly slice the pork. Arrange the fennel and garlic on a platter and top with the pork. Garnish with parsley and serve the sauce on the side.