Pat the green leaf lettuce dry with a paper towel and tear into large pieces.

In a bowl, mix the beef with the seasoning ingredients (sake, sugar, soy sauce, garlic, ginger).

In another bowl, crack the egg, add a pinch of salt, and mix well.

Heat 1/2 tbsp of salad oil in a frying pan over medium heat. Pour in the egg mixture and stir until it becomes scrambled and crumbly. Remove and let cool.

In the same pan, heat 1/2 tbsp of salad oil over medium heat. Add the beef and cook until browned on both sides. Remove and let cool.

In a bowl, mix the cooked rice with the sesame seeds.

Place a sheet of roasted seaweed on plastic wrap in a diamond shape. Add 1/4 of the rice, 1 lettuce leaf, half the beef, half the scrambled egg, and another 1/4 of the rice. Fold the corners of the seaweed to the center to form a square. Repeat to make two onigirazu.