Dice, chop, and prep all the ingredients.
In a small bowl, combine cornstarch, stock/water, and sesame oil. Stir well to mix into the slurry sauce.
Bring a saucepan or wok over medium/high heat, when hot, add butter.
Twirl butter around the pan with your spatula to coat the surface.
When butter melt, stir in garlic, saute to brown for a couple of seconds.
Add all the shrimp, stir well until all the shrimp are starting to change their color.
Stir in black bean sauce, oyster sauce, diced onion, and ground pepper. Keep on stirring.
When all the shrimps are done (do not over cook), pour in the slurry sauce.
Keep stirring constantly to thicken the sauce, then sprinkle in the chopped mint leaves.
Stir to mix and immediately remove the saucepan from heat.
Serve hot immediately with some rice or pasta as a side.