Place beef tongue in a large pot and add enough water to cover the tongue. Bring the water to a boil over medium-high heat then reduce heat to low and simmer the tongue for 2 hours. Note: you can use a pressure cooker or instant-pot to cook the tongue as well. Reduce cooking time to 45 minutes.
Transfer the cooked tongue to a work surface and cool 10-15 minutes, until east to handle. Peel outer layer of skin from beef tongue. Slice the tongue into thin pieces and cool completely.
Combine all of the marinade ingredients together in a bowl or large ziploc bag and add the cooled tongue slices. Flip slices to cover both sides with marinade then cover and place in the refrigerator for at least 1 hour.
When ready to serve, heat a neutral oil such as vegetable or canola oil in a heavy bottom saucepan. Cook the marinated tongue slices for 2 minutes on each side, until slightly charred around the edges. The tongue can also be broiled or grilled.
Serve tongue bulgogi in a lettuce wrap with white rice and a garnish of sesame seeds, scallions and sriracha.