Generously season the top of the meat pieces with salt and pepper; set aside.
In a large skillet over medium-high, add oil and when hot, add beef, seasoned side down; season the top with salt and pepper. Quickly sear meat pieces on all sides (don’t forget to season each side before turning).
Transfer to crock pot, including any accumulated juices. Add onion, poblano pepper and jalapeño pepper; sprinkle on Old El Paso Taco seasoning; set aside.
In the jar of a blender, add all the sauce ingredients and process until smooth.
Transfer the sauce to a large measuring cup (it makes approximately 2 ½ cups) and pour 1 ½ cups over the beef; reserve 1 cup for later.
Add bay leaves, close the lid and set the heat on “Low”; cook for 8:30 hours (high for 4 to 6 hours), or until the meat is tender.
When time is up, remove the bay leaves and discard them.
Working with one piece of beef at a time, shred the meat, using two forks. Return the meat to crock pot while working with the others (keep the lid closed).
Add the reserved 1 cup of sauce and stir well. Cover, set the heat to “Low” and the timer for 30 minutes to warm up the sauce. Use a slotted spoon when serving.