Add the ribs to a gallon size ziplock bag.
In a large glass measuring cup or bowl combine the brown sugar, 1 cup soy sauce, water, mirin, green onions, garlic, ginger, toasted sesame oil and pepper. Pour the marinade over the ribs and seal the bag. Place the ribs in the fridge and marinate 4 hours or overnight.
The next morning, preheat the oven to 325 degrees F.
Add the ribs and the marinade to a large roasting pan. Cover the pan tightly with foil and bake the ribs for 2 to 2 1/2 hours or until the ribs are tender. While the ribs bake is when I like to make the slaw + relish (recipes below)
Remove the ribs from the roasting pan and strain the remaining liquid through a fine mesh strainer and right into a sauce pot. To the pot add the [gojujang | http://www.amazon.com/Sunchang-500g-Gochujang/dp/B002WTE0MQ/ref=sr_1_1?ie=UTF8&qid=1397010543&sr=8-1&keywords=gojujang] and ketchup. Bring the sauce to a boil and simmer over medium heat until the sauce has reduced by half and thickened, about 10 minutes. Remove the BBQ sauce from the heat.
Preheat the grill to medium high heat.
Brush the ribs all over with the BBQ sauce and grill the ribs for about 7-8 minutes per side. Be careful when flipping as the ribs will be tender. Remove the ribs and allow to cool 5 minutes. Shred the meat with two forks. Stuff the meat inside the buns, top with swiss cheese, peach relish (below) and the Korean Slaw (below). Sprinkle with cotija cheese. EAT.