Many restaurants actually serve a "light" version of the Tso sauce, and I have a pretty strong feeling that's what you're used to.
To make the light version, you use 3x the corn starch and add 1/2 cup of the base liquid (usually chicken broth).
The hint of sesame almost certainly came from toasted sesame oil, my favourite "secret ingredient" that goes into just about every Asian stir-fry.
To get a more consistent flavour for the sauce, instead of using "minced" garlic, you might want to grate it using a fine rasp, if you have one. This will definitely help to bring out the flavour of the garlic and subsequently the spiciness of the sauce.
Grated orange zest is another common additive, and although it's traditionally labeled as a different recipe ("General Tso's Chicken with Orange"), some restaurants sneak it into the regular recipe. If you remember any hint of orange, try adding about 1 tsp of this.
Finally, if we're trying to recreate a recipe from an American Chinese restaurant, it's very likely they used some MSG. You can leave it out, but we all know how much of a flavour enhancer it is.
I don't actually have an exact recipe kicking around, but adapting these changes to the "traditional" recipe, it should look something like this:
- 1 cup chicken broth
- 1/4 cup soy sauce
- 2-3 tbsp rice wine or sherry (to taste)
- 1 tsp toasted sesame oil
- 1/4 cup sugar
- 1 tsp MSG (optional)
- 1 1/2 tbsp rice vinegar
- 3 tbsp tapioca flour or corn starch
- 6-10 dried red chilies
- 1 tbsp minced ginger
- 1 tbsp grated or finely minced garlic
I'm going to skip the ingredients and preparation for the fried chicken itself, since that's pretty straightforward and no different from any of the "normal" Tso recipes. So let's assume that part has already been done. Here's how I'd make the sauce and finish it off:
Combine the chicken broth, soy sauce, rice wine, sesame oil, sugar, [MSG], and rice vinegar. Make sure that the sugar is completely dissolved.
Add tapioca to the soy sauce mix and dissolve.
Heat a few tbsp of oil in your wok and start frying up the chilies. The longer you fry them, the hotter the final dish will be, so adjust the timing to taste. Many restaurants skimp here, and either don't use enough chilies or don't fry for anywhere near long enough. You're looking for a deep, dark red, almost black colour for optimum heat.
Add the soy sauce / tapioca mix, garlic and ginger, and stir.
Once thickened, add the chicken and serve with the broccoli. (You most likely got it steamed, that's how it looks in the picture, although my choice would be to stir-fry it with some red pepper flakes.)
I can't promise you that this will be identical to what you got in the restaurants, as I haven't been to those restaurants, but hopefully this sounds a lot closer to what you had than the garbage you traditionally find in lower-end restaurants and on recipe sites.
Update: After reading some of the results of this experiment, I would add the following (better late than never, right?):
The above ratio of starch to water will result in a very thick, almost paste-like consistency. That's intentional, but if you want something more "saucy", i.e. to put on rice, then don't triple the starch, especially if you're using tapioca. 2 tbsp should be sufficient. At the same time, keep in mind that it's always easier to dilute a sauce that's too thick than it is to thicken it in the wok once it's already hot.
If you're finding that it's still not spicy enough (I, too, like my spicy dishes blazing hot), then try including any or all of the following in the sauce:
- 1 tsp chili oil
- 1 tsp hot chili sauce (proper chili sauce like sriracha, not tabasco)
- 2-3 fresh red chilies, cut into rings, with seeds (caution: very hot)