Cut beef roast into 2 to 3" pieces; season with pepper. Coat large nonstick skillet with nonstick spray; heat over medium until hot. Add half of beef; brown evenly, 3 to 4 minutes per side.
Transfer beef to slow cooker. Repeat with remaining beef.
Add stock to skillet; cook and stir 1 to 2 minutes or until browned bits attached to skillet are dissolved. Stir in gochujang, garlic, fish sauce, hoisin sauce and sambal. Pour mixture into slow cooker. Cover and cook on HIGH 4 hours or LOW 6 hours or until roast is fork-tender.
Meanwhile, combine cucumber, carrots, ginger and vinegar in small bowl. Cover and refrigerate.
Cook's Tip: Roasted Beef Stock:
Preheat oven to 475°F. Place 6 to 8 pounds beef Bones, 2 cups diced yellow onions, 1 cup sliced carrots and 1/2 cup sliced celery in roasting pan. Roast in 475°F oven 45 minutes or until browned, turning once. Spread 2 tablespoons tomato paste over bones; roast 15 minutes. Remove from oven; drain fat.
Place bones and vegetables in large stock pot. Scrape bottom of roasting pan to loosen any brown bits; add to stock pot. Add 1 gallon water; bring to boil. Add 10 black peppercorns, 3 to 4 sprigs fresh parsley, 2 cloves garlic, 2 sprigs fresh thyme and 2 bay leaves to stock pot. Simmer stock 8 to 10 hours, occasionally skimming off impurities.
Remove stock pot from heat; cool 15 minutes. Strain stock through cheesecloth-lined colander into large bowl.
Remove roast from slow cooker. Skim fat from cooking liquid. Reserve 1 tablespoon cooking liquid. Shred beef with 2 forks. Combine shredded beef, remaining cooking liquid and lime juice. Season with salt and pepper, as desired. Cover; keep warm.
Combine Beef Chopped Liver, reserved 1 tablespoon cooking liquid, plum sauce and Cognac in small bowl; mix well. Season with salt, as desired. Using a whisk, whip cream in small deep bowl to soft peaks. Fold cream into liver mixture. Cover and refrigerate until ready to serve.
Cook's Tip: Classic Chopped Beef Liver:
Place 1 pound beef liver in medium bowl; add 2 cups 1% low-fat milk. Cover and refrigerate 30 minutes.
Preheat broiler. Remove liver from milk; discard milk. Place liver on rack in foil-lined broiler pan so surface of beef is 3 to 4 inches from heat. Broil 9 to 12 minutes until instant-read thermometer inserted horizontally into center registers 160°F, turning once.
Place liver in food processor bowl. Pulse on and off until finely chopped; remove liver from processor. Add 1 hard-cooked egg, 2 tablespoons minced onion and 1/2 teaspoon minced garlic to food processor; pulse on and off until paste forms. Return liver to food processor; add 2 tablespoons lard. Pulse on and off until blended. Add 1 teaspoon chopped fresh parsley leaves; pulse until mixture is smooth is smooth. Season with salt and pepper, as desired.
Place liver mixture into medium bowl; cover and refrigerate for at least 1 hour.
Spread 2 teaspoons liver mixture evenly over cut sides of each roll. Divide shredded beef evenly among rolls; top with cucumber mixture. Top with additional pickled onions, radishes, carrot, basil, mint, jalapeño peppers, cilantro and lime wedges, if desired.
Cook's Tip: Optional Toppings include pickled onions, sliced radishes, shredded carrots, fresh Thai basil leaves, fresh mint leaves, thinly sliced jalapeño peppers, chopped fresh cilantro leaves and lime wedges.