Step 1: Heat 3 tablespoons of cooking oil in a large wok or deep pan over medium-low heat. Add 4 tablespoons of chunjang. Fry the chunjang, stirring constantly, for 5-7 minutes until it becomes glossy and fragrant. This crucial step removes bitterness and develops flavor. Remove the fried chunjang and oil to a small bowl and set aside.
Step 2: In the same wok (or add a little fresh oil if needed), add the diced pork. Cook over medium-high heat until browned and cooked through, about 5-7 minutes. Drain any excess fat, leaving about 1-2 tablespoons in the pan.
Step 3: Add the minced garlic and ginger to the pan with the pork. Sauté for 1 minute until fragrant. Then, add the diced onions. Cook until softened and translucent, about 5-8 minutes.
Step 4: Add the diced potatoes to the pan and cook for 3-5 minutes, stirring occasionally. Then, add the diced zucchini and cook for another 2-3 minutes. You want the vegetables to be slightly tender but still have a bit of bite.
Step 5: Stir in the fried chunjang mixture, ensuring all ingredients are well coated. Cook for 1-2 minutes, allowing the flavors to meld.
Step 6: Pour in the chicken or vegetable broth. Bring the mixture to a simmer. Reduce heat to low, cover, and let it cook for 10-15 minutes, or until the potatoes are tender. This slow simmer allows the flavors to deepen.
Step 7: In a small bowl, whisk together the cornstarch and 2 tablespoons of cold water to create a slurry. Slowly add the slurry to the simmering sauce, stirring constantly, until the sauce thickens to your desired consistency. It should be thick enough to coat a spoon.
Step 8: Stir in the sugar and a splash of sesame oil. Taste and adjust seasonings as needed. If it’s too salty, add a little more sugar or broth.
Step 9: Divide the cooked noodles among serving bowls. Spoon a generous amount of the rich black bean sauce over the noodles. Garnish with fresh julienned cucumber, a fried egg, or pickled radish if desired. Serve immediately and enjoy!