Partially thaw the sirloin in the refrigerator (our deep freezer is set at -5 f, and our refrigerator at 34, so for us, it takes about 12 hours to half-thaw).
Cut the meat from the bone, and remove large deposits of extra fat. Reserve the bones for making stock.
Slice the meat into strips 1/4″ to 3/8″ wide and about 2″ long. Return to refrigerator to finish thawing (about another 12 hours).
Cook the meat
Slice the onion, and layer about 3/4 of it on the bottom of your crock pot. Dice the garlic, and sprinkle it around the pot as well. Then layer the beef over the onions and garlic.
Sprinkle all of the dry spices and herbs over the meat, more or less evenly.
In a small bowl, add the bourbon, soy sauce, mustard, Worcestershire sauce, and Tabasco sauce. Whisk to combine, then pour over the beef.
Pour the beer over the beef, add the bouillon, cover the crock pot, and let it cook on low for about 8 hours.
Make the sandwiches
Stir the meat mixture, turn the crock pot to high, and let cook with the lid off for about 5 minutes.
Slice the peppers. Cut the baguettes in half, then slice the halves lengthwise. Line the bottom halves up on a baking sheet.
Put a layer of Swiss cheese on the bottom half of each sandwich. Then layer with the meat mixture. Add peppers and reserved slices of onions on top, then a layer of provolone cheese.
Place the bottom halves of the sandwiches under the broiler, and watch closely. When the cheese has begun to melt, but not yet brown, add the tops, upside-down, to the broiler as well (don’t add them at first, or they’ll burn)
When the cheese and veggies start turning golden brown, remove from the broiler. Add the top. For those who like an au jus, spoon some of the sauce from the crockpot into a ramekin.