Mince the garlic and slice the tomato into discs. Add the garlic, soy sauce, vinegar, sugar, honey and half of the water to a frying pan set over a medium heat. Simmer for 3 mins.
Make a slurry with the cornstarch and the remaining water, then mix thoroughly. Turn the heat off the pan and slowly pour in the slurry while stirring. It should be smooth with the consistency of gravy. If too thin, add more slurry; if too thick, add a little cold water. Set aside while you make the rest of the sandwich.
Heat a new frying pan over a medium heat, then add the butter and gently toast the brioche on both sides (around 1 min per side). Keep an eye out so they don’t burn. Remove from the pan and add a slice of cheese to each slice.
Turn the heat up to high and add a splash of oil to the same pan. Season the steak with salt. Add the steak to the pan and cook for 2 mins per side for medium-rare. Remove and rest on a plate.
Slice the steak into thin strips, removing any bits of fat. Divide the steak slices between two slices of brioche. Generously coat with the sauce. Add tomato slices followed by a handful of rocket.
Press down with another slice of bread to complete the sandwich. Cut in half and enjoy!
