Garlic Sauce
To make the sauce, combine all ingredients in a blender and blend until smooth. Set aside.
Stir-fry
In a large skillet, add sesame oil on medium-high heat (not toasted sesame oil - just regular sesame oil).
Add onions, bell peppers, broccoli and mushrooms, season with salt and pepper, and cook until they get caramelized in colour and are cooked through but still slightly crunchy from the outside, about 8 minutes.
Transfer vegetables to a plate and set aside.
Now change heat to medium, season sliced chicken with salt and pepper and add to the hot skillet. Cook until cooked through, about 8-10 minutes. Alternatively, while vegetables are cooking, use a different skillet to cook the chicken, then add chicken to the vegetable skillet.
Transfer vegetables back to the pan with the chicken and pour in all the sauce, stir, turn off heat and enjoy on its own or serve with noodles or rice.