Every time I get Chinese takeaway the black bean sauce is thick, tasty and plentiful, but every time I see a recipe for a black bean dish it has a thin sauce. This is my attempt at fixing it, the way I've done a few things is fairly unconventional, but makes it super easy to put together once the sauce has been made and you don't need to worry about the meat overcooking while the sauce thickens. I was originally going to use a can of mixed Asian stir-fry veggies in the sauce but the store didn't have any so I've listed what I used but go ahead and use whatever sounds good. If using fresh you can also saute at the same time as the onion and garlic. Note the recipe gives quite a strong and salty sauce that is great soaked up with with plenty of rice, if you like a fairly mild black bean sauce reduce the black bean paste for the sauce to 1/4 cup.