Prepare your veggies by cutting them down into 1/2 inch squares.
Score your pork belly then cut them into 1 inch slices. Let them come to room temperature before cooking.
Bring a non-stick pan to medium heat and cook the pork belly until both sides are lightly browned. There should be a good amount of oil rendered out- leave it.
Add the onions and potatoes. Sauté until onions become translucent, about 2-3 minutes.
Add the zucchini and cabbage. Sauté another 2-3 minutes.
Make a hole in the center and add 3 tbsp oil. Put the black bean paste on top of the oil and spread evenly. Tilt the pan back and forth to bring more oil to the center, and continue frying the paste in it for about 3 minutes.
Mix everything together and continue to fry for another 2-3 minutes, then add the ginger, black pepper, and sugar.Note: If you don't like it too sweet, start with 1 tbsp sugar and gradually add more if needed. I added 3 tbsp to mine- my husband likes it sweet.
Add the beef broth and mix until combined. At this point, add the msg if you're using it.
Add the corn starch slurry and continue mixing until the sauce has almost thickened to your desired consistency. I recommend getting it to a point where it is slightly too thin for your liking- it will thicken even more once you turn off the heat.
Ladle the sauce over jajang noodles or rice. Drizzle over a tiny bit of sesame oil, then garnish with thinly sliced cucumber and sesame seeds. Serve with danmuji (yellow pickled radish).