Start by making the Yakiniku sauce. Add sliced chili pepper and all the other ingredients, except sesame oil, into a pot then cook and stir until it starts to boil. Add the sesame oil and stir for another 2 minutes.
Slice onions into 1/2’’ thick and pepper into ½’’ width. Slice Kabocha pumpkin and zucchini into ½’’ thick. Cut off the stems from mushrooms and slice them in three thin slices each.
Boil the eggs for about 5 minutes and cool them off under cold water. Peel them and set aside.
Heat the vegetable oil on the teppan (or skillet) at high heat. Start by grilling the vegetables because they will take longer than the meat, then cook the sliced meat alongside the vegetables on the teppan (or use a separate skillet for the meat) and add the Yakiniku sauce to the meat.
The vegetables should be done after about 12 minutes and the meat in about 8. Use the grill scrapers to move around the vegetables and meat a few times during this time to make sure every side gets evenly grilled.
Serve the meat and vegetables in a bowl with some noodles or steamed rice underneath and add the cooked egg, you can halve them per bowl, and add freshly chopped cilantro.