Step 1

In a small food processor combine the garlic, anchovies, rosemary, salt and pepper. Add the olive oil and process until it forms a paste, scraping down the sides. Remove the blade and use a fork or spoon to stir in the mustard. Rub the paste all over the pork shoulder, loosely cover it with plastic wrap, and refrigerate from 2 to 24 hours.

Step 2

Preheat the oven to 450°F and bring the pork to room temperature while the oven heats. Place the pork in a shallow roasting pan and roast, uncovered, for 30 minutes, until the top starts to brown a bit. Turn the heat down to 250°F and continue to cook, uncovered, for 6 to 8 hours until the middle of the roast registers 180°F. on an internal thermometer, and as you slide the thermometer in you can feel that the meat is very tender throughout. If there are juices in the pan (and I have found that sometimes there are and sometimes none) pour off the juices from the pan into a heatproof container, like a Pyrex measuring cup. Place this in the fridge, where the fat will rise to the top, while the meat rests.

Step 3

When the meat is cooked, if you think that the outside of the roast could use a bit more crust/brownness, turn the heat back up to 450°F and let it cook for another 15 to 20 minutes, to give the outside a bit more of a crunchy texture.

Step 4

Remove from the oven and let sit for about 20 minutes. Spoon the fat off the reserved juices in the fridge and pour the cooking juices into a serving pitcher or bowl (warm it a bit in the microwave or in a small pot if you like). Slice the pork as thinly or thickly as you like, knowing the meat will fall apart at least slightly. Sprinkle the sliced meat with a bit of salt before serving, and pass the pan juices on the side to drizzle over.