In a skillet over high heat, brown the ribs (1-2 minutes per side).
In a large, oven-safe pot, place the ribs, caramelized onions, garlic, taco seasoning, flour, butter, beer, beef broth, rosemary, and thyme. Stir thoroughly, and cover the pot.
Bake on the center rack for 2½ hours. Keep the oven hot after removing the pot.
Take the ribs from the pot, remove the meat from the bones, and set it aside.
Over medium heat, reduce the volume of the remaining liquid in the pot by half. It should have the consistency of very thick barbecue sauce, so it will cling well to the meat; a runny sauce would make your chips soggy. Decant the sauce into a mixing bowl.
Add the meat to the bowl, and thoroughly mix to coat the meat with sauce.
On a large baking sheet, spread out the nacho chips evenly. Sprinkle half the shredded cheddar over the top; then, the meat in sauce. Top with the rest of the cheddar, and bake for 10 minutes.
Add the guacamole and sour cream. Garnish your Braised Beef Nachos with the chopped olives, chives, and jalapeños, and enjoy!