1. Prepare Slow Cooker and Ingredients:
- Halve and thinly slice the large sweet onion. Place the sliced onion in the bottom of a 5-quart slow cooker, spreading it out to create a bed for the roast.
- If your beef sirloin tip roast is very large, cut it in half so it fits comfortably in the slow cooker. Place the roast pieces directly on top of the sliced onion.
- In a small bowl, combine the chipotle salsa, beer (or nonalcoholic beer/broth), and the dry Lipton beefy onion soup mix. Stir well to combine these sauce ingredients.
- Pour this prepared salsa mixture evenly over the top of the roast in the slow cooker.
2. Slow Cook the Beef:
- Cover the slow cooker securely with its lid.
- Cook on the LOW setting for 7-8 hours. The beef is done when it is very tender and easily shreds with a fork. An internal temperature check isn’t strictly necessary for shredding, but if desired for safety, it should reach well above 165°F (likely closer to 200°F for easy shredding).
3. Shred Beef and Combine with Juices:
- Once the beef is fall-apart tender, carefully remove the roast pieces from the slow cooker using tongs or large forks. Place them on a large cutting board or platter, leaving the cooking liquid and onions in the slow cooker.
- Using two forks, shred the cooked beef. Discard any large pieces of fat you may encounter.
- Return the shredded beef to the slow cooker with the flavorful cooking juices and onions.
- Stir everything together well to ensure the shredded beef is thoroughly coated with the sauce.
- Cover and let it heat through on LOW or WARM setting for another 15-30 minutes, allowing the shredded beef to absorb more of the delicious sauce.
4. Assemble Sandwiches and Serve:
- While the shredded beef heats through, split your Kaiser rolls. Toasting them lightly is highly recommended for best texture and to prevent sogginess.
- Using a slotted spoon (to allow some of the thinner juices to drain if desired, or a regular spoon if you like it extra saucy), spoon a generous portion of the hot shredded Chipotle Beef mixture onto the bottom half of each toasted Kaiser roll.
- Place the top half of the roll over the filling.
- Serve the Chipotle Beef Sandwiches immediately while warm. Enjoy!