Heat a large pot or wok over medium heat and add 1 tablespoon vegetable oil.
Add in the black bean paste and fry until aromatic, a few minutes.
Transfer the paste to a bowl and add in the remaining 1 tablespoon oil.
Add in the onions and stir fry for 1-2 minutes, until fragrant.
Next, add in the cubed pork and cooked until almost cooked through, about 3-4 minutes.
Add in the zucchini, diced potato, and fried black bean paste.
Stir to coat everything with the paste.
Pour in about ½ C of water/stock, or enough to cover the veggies and pork and bring to a boil.
Cover with a lid and lower to a simmer. Cook until the potatoes have softened, about 10 minutes.
In the meantime, mix potato starch with cold water in a small bowl to a make slurry.
Pour the starch slurry into the mixture and stir.
Bring it up to a boil, and check the consistency. It will thicken -- if it's too thick, thin it out with additional water, 1 tablespoon at a time.
Once it's thickened to your liking, remove from heat.
Add in a drizzle of sesame oil and serve the sauce with cooked wheat noodles.