Season the short ribs with 2 teaspoons kosher salt and 1 teaspoon ground black pepper. Dredge the seasoned ribs in the flour until lightly coated, shaking off excess.
Heat a dutch oven over mid-high heat and add 1 tablespoon olive oil and 1 tablespoon butter. Allow the fat to heat up just a bit, but don’t burn it.
Add the ribs in a single layer and brown on all sides. This will take 4-5 minutes on each side to brown, but it is worth it. The browning definitely adds flavor.
When all the ribs are browned, remove them from the pan and set aside. Reduce the heat to medium, and add the sliced onion and 1 tablespoon freshly minced garlic to the pan. Cook, stirring, for about minute and then pour in the can of beer.
Stir, being sure to scrape all the browned bits from the bottom of the pan. Add the cup hot water and stir to combine. Bring to a gentle boil.
Return the beef short ribs to the pan, cover and reduce heat. Allow the ribs to simmer until very tender – about 2 hours.
Next you’ll want to caramelize your onions. Heat a skillet over medium heat and melt 2 tablespoons butter. Add the sliced onions and a pinch of salt and stir, cooking, until they are tender.
Reduce the heat to mid-low and continue to cook until the onions are a nice caramel color, stirring occasionally. This will take about 30-45 minutes depending on how high your heat is.
When the short ribs are fall-off-the-bone tender, go ahead and remove the bones and discard. Divide the beef among the four toasted buns and top with a spoonful of the sauce in which the ribs cooked.
Then top with caramelized onions and the shredded cheese. Pop the sandwich back under the broiler to melt the cheese and enjoy!