In a large heavy-bottomed pot, melt butter over medium heat and sauté garlic and onion. Add beer, chicken broth, 1/3 cup (80ml) maple syrup, mustard, spices and pepper to taste. Mix well to incorporate the mustard, and bring to a boil.
Place smoked shoulder picnic in pot. Bring to a boil, cover and simmer for 90 minutes or until meat is tender.
Preheat oven to 200°C (400°F).
Remove pork shoulder from saucepan, remove netting around the meat, and place meat in an ovenproof dish.
Place saucepan back on burner and reduce broth by half. Add remaining 1/4 cup of maple syrup. Baste meat with reduced broth and place in oven for 15 to 20 minutes. Baste frequently during cooking. Slice smoked shoulder picnic ham and serve with your choice of vegetables.