Method

Generously season pork on all sides with salt and pepper.

Place a heavy-bottomed saucepan that is just large enough to hold the pork over medium-high heat. Add oil and heat. Add pork and brown on all sides, turning only as necessary. Transfer pork to a plate; carefully pour off and discard the fat in the pan.

In a small pot over medium heat, warm milk, but don't let it boil.

Return the pork's pan to medium heat, add butter and heat until melted. When foam subsides, add garlic and, if using, the sage and cook just until garlic is softened but not browned. Return pork to pan and add enough hot milk to submerge pork by at least three-quarters. Increase heat to medium-high and bring milk to boil. Immediately reduce heat to medium-low, add lemon zest, cover partially and simmer gently for 1 1/2 to 2 hours or until internal temperature of the pork is 155 degrees. Note: Resist the temptation to disturb meat while cooking. The milk will curdle and form brown nuggets; don't panic, this is what you want as they taste nutty, sweet and delicious.

Let the meat rest under tented foil for 10-15 minutes before serving, reducing the milk sauce a little more during this time if you desire. Slice the pork thickly, and spoon cooking sauce over top of pork to serve.