Take whole shallots and thinly slice on a mandolin. Next, coat with a touch of buttermilk, just enough to make shallots a little moist. Dry and coat with flour, making sure to separate all clumps. Fry the shallots until golden brown and reserve for later use.
For the braising liquid: Heat the olive oil in a saucepot. Add the carrots, celery, garlic, thyme, shallots and onions. Cook until the onions begin to brown, then turn down the heat and add in half of the tomato paste and cook until it turns to a rust color.
Add in the red wine and reduce for 3 to 5 minutes, making sure not to burn anything in pan.
For the short ribs: Preheat the oven to 350 degrees F. Heat a pan over medium-high heat, with enough olive oil to cover the bottom of the pan.
Mix the salt, cumin, five-spice powder and pepper. Coat all sides of the short ribs with the spice rub, then place in the preheated pan and sear until golden brown on all sides.
Place the short ribs in a braising pan or cake pan and cover with the braising liquid. Cover very tightly with foil and cook in the oven until fork tender, 2 1/2 to 3 1/2 hours, depending on the thickness of the meat.
When the meat is done, let it cool in the liquid. Remove the meat from the liquid, and then pull apart with a fork, reserving the liquid.
Heat a pan and place some of the pulled short rib inside. Season with salt and pepper if needed and start adding in some of the reserved liquid to keep the meat moist. Add some cheese and let melt. You can flip the pile to cheese-side down, to grill the cheese if you like.
Cut the bread into 8 slices. To build the sandwich, place the short ribs on the bottom piece of bread, topped with arugula and some fried shallots.