Heat the oil in a large non-stick frying pan over medium-high heat. Add the beef and cook, turning often, for 10 minutes or until browned. Transfer to the slow cooker.
Place the stock, soy sauce, mirin, sake, sugar, garlic and ginger in a jug. Stir to dissolve the sugar. Pour over the beef. Cover and cook on Low, turning the meat occasionally, for 8 hours or until very tender.
Transfer the beef to a large plate. Use 2 forks to coarsely shred. Return the beef to the slow cooker to cover in sauce. Divide beef among serving plates. Sprinkle with sesame seeds and shallots. Serve with sliced chilli and rice.
