Take your meat out to defrost, if frozen, well before dinner or lunch time. Don't forget!

In a small (deep, not shallow) bowl or cup, pour your soy sauce, chili flakes, brown sugar, rice vinegar, and mirin. Droplets of vinegar. It is Powerful. Don't add a lot. Mix this well, and don't freak out if the sugar stays solid. It's fine. Just give it a stir again before adding it and scrape all the sugar sludge out of the bowl when you use it.

In, to be specific, a medium short handled soup pot, put your sesame oil, onions, bell peppers, garlic, mixed veggies, and broccoli. Don't be shy with the salt and pepper, because the meat and your rice or pasta will drown it out. Stir and cook until the onions are glossy and translucent, and the broccoli stems are somewhat soft.

Crumble in your bouillon cubes (really like powder it between your fingers, you don't want lumps), and maybe add some water to help steam this before adding in your meat and soy sauce mixture, and cook until the beef is browned evenly, the sugar is melted, and the veggies coated with the soy sauce mixture.

You can add your pasta or rice into the dish at this point and mix until coated, before plating. I recommend mixing the pasta in, but not the rice. The rice tends to absorb all the flavoring, so you might have to make a double soy sauce mix to make sure there aren't any "dry" patches. Plating the rice and then using the stir fry as a topping tends to work better.