Step 1

To make the spicy mayonnaise: In a small bowl, whisk together mayonnaise, sour cream, gochujang, lime juice, and sesame oil. Transfer to an airtight container and place in refrigerator until ready to use.

Step 2

To make the tuna: In a small bowl, mix together gochugaru, sesame seeds, salt, pepper, and garlic powder. Season tuna all over with seasoning mixture. Light one chimney 2/3 full of charcoal.When all the charcoal is lit and covered with gray ash, place a small grill grate on top of chimney. Brush each side of tuna with oil and place on top of grate. Cook until the first side is browned and easily releases from grate, about 1 minute. Flip tuna over and grill until second side with well browned and easily releases form grate, about 1 minute more, Transfer tuna to a cutting board and cut into slices about 1/2-inch thick and 2 inches wide.

Step 3

To make the buns: Steam buns in a bamboo steamer or in the microwave on a large plate under a damp towel. Spread a layer of the spicy mayo over entire inside of each bun and top with a slice of avocado and tuna followed by a sprinkling of fried shallots, scallions, cilantro, and a few chili strips. Serve immediately.