From Erin (from Don't Panic More Dinner's in the Freezer)
1 medium onion, halved
1 1/2 lbs beef roast, cubed
1/2 lb. pork roast, cubed
1 26oz bottle ketchup
2 tbsp dry mustard
2 tbsp white vinegar
2 tbsp sugar
1 tsp salt
2 tbsp whole pickling spice in a tea ball or tied in a cloth bag
yields 9-12 sandwiches
Meat: Place onion halves, beef, and pork in the crockpot with about a cup of water on low 4-6 hours. Remove cooked meat from liquid and shred or chop in food processor.
Sauce: Combine all sauce ingredients in large saucepan; simmer for 30 minutes. Add shredded meat to sauce. Simmer an additional 20 minutes. Remove pickling spice bag. Cool completely and freeze in a freezer bag.
Thaw bbq to a slushy consistency and reheat in saucepan. Serve on warm rolls or buns.