1. Cook rice
Rinse the rice until the water runs clear. Put in a small saucepan with 250ml (1 cup) water, cover and bring to a simmer over medium heat. Reduce the heat to low and cook for 12 mins or until tender and the water is absorbed. Turn off the heat and stand, covered, for at least 5 mins.
2. Prep ingredients
Meanwhile, thinly slice the cucumber. Thinly slice the spring onions on an angle. Thinly slice the cabbage with a sharp knife or mandoline. Coarsely grate the cheese. Combine 2 tsp white vinegar and a pinch of salt in a bowl. Add the cucumber and half the sesame seeds and toss to coat. Set aside to pickle, tossing occasionally, until needed.
3. Soften cabbage
Preheat the grill to high. Put 1 tbs tonkatsu sauce, 2 eggs, 1 tsp soy sauce and 2 tsp water in a bowl and whisk to combine. Heat 1 tbs vegetable oil in a medium deep ovenproof frypan (see Kitchen hack) over medium-high heat. Cook the cabbage, stirring occasionally, for 3 mins or until softened. Remove the pan from the heat.
4. Grill omelette
Pour the egg mixture over the cabbage. Scatter over the cheese and half the spring onion. Grill for 2-3 mins until the cheese is melted and the egg is set. Transfer to a board and cut into 3cm squares.
5. Serve up
Divide the rice, omelette and drained pickled cucumber among plates. Drizzle with the mayonnaise and remaining tonkatsu sauce, then scatter over the remaining sesame seeds and remaining spring onion. Or, pop everything on the table for everyone to help themselves. Enjoy!
6. Kitchen hack
Your frypan will need an ovenproof handle to cook under the grill. If you don't have one, wrap the handle of a regular frypan with a double layer of foil, or transfer the cabbage to an ovenproof dish before adding the egg mixture.