Begin by butterflying the steak. Place the flank steak flat on a large cutting board. Select a sharp knife with a long thin blade. Place your left (or right, if you’re left-handed) hand on top of the steak. Starting at the long edge of the steak, slice almost through it, slicing parallel to the board. Leave the steak “hinged” along the opposite long side so that it can open up to twice its original size. For safety’s sake, be extremely careful to keep the blade of the knife equidistant between the cutting board and the palm of your hand. When the steak has been “butterflied”, open it up pound it with a meat mallet, heavy frying pan, or a rolling pin. A few good whacks should make it nice and thin; set aside. Preheat oven to 350 degrees.
Combine the shredded cheese, cornbread, green onions and Roasted Tomatillo Pepper Sauce in a bowl, stirring to blend well and moisten the cornbread pieces. Spread the cheese mixture on the meat. Beginning at a long side, roll the meat up like a jelly roll. Tie securely with cotton kitchen twine along the length of the roll. Combine a portion of the Chuck Wagon Steak Seasoning with just enough of the olive oil to make a spreadable paste. Spread the rub all over the rolled and tied meat. In a large heavy-bottomed, ovenproof skillet with high sides or a braising pan, heat about 3 tablespoons of the olive oil until hot. Sear the meat over medium-high heat to brown on all sides. Remove from heat and add the beef broth and Shiner Bock. Cover the pan and braise in preheated oven for 1-1/2 hours, or until meat is very tender.
Remove meat to a cutting board. Reserve pan juices. Cover meat loosely with foil and allow the meat to rest for 10 minutes before slicing. Return the pan to medium-high heat and stir in the Peach Pecan Barbecue Sauce. Cook, stirring often, until reduced by half, about 10 minutes. Slice the meat into 1-inch thick rounds. Arrange the slices on a serving platter and drizzle some of the sauce over the meat. Pass the remaining sauce separately.