In a skillet over medium heat, toast the fennel seeds for 2-3 minutes with a touch of oil.
Place the garlic, shallots, toasted fennel seeds, tomato paste, salt and pepper in a food processor. Run until a thick paste forms, adding some of the oil as you process.
Grab a large roasting pan, crockpot or Dutch oven. Rub 2/3 of paste all over the pork shoulder and place into your vessel. Bake (or cook on high setting) for 30 minutes, then stir in the remaining paste with the beer and vinegar, pouring it in carefully.
Turn the oven down to 250F and cook for 10 hours (good night), or, if using a crockpot, turn down to low setting for about 12 hours.