Chadol Jjamppong (Korean Spicy Noodle Soup with Beef Brisket)

Ingredients

• 1 tbsp oyster sauce
• 1 tbsp soy sauce
• 4 garlic cloves
• Kosher salt, to taste
• 1 yellow onion
• Small pinch of MSG (optional)
• 2 green onions, divided
• 1/2 tsp white pepper (or black pepper)
• 1 tbsp chicken bouillon powder
• 2 Napa cabbage leaves (or green cabbage, baby bok choy)
• 1 baby bok choy
• 2 tbsp neutral-tasting oil (canola, grapeseed, vegetable oil, etc.)
• 1-2 Vietnamese dried chilies (or peperoncino) (optional)
• 8.8 oz (250g) (frozen) thinly sliced beef brisket (or slice it yourself)
• 4.5 cups (1,080ml) water, divided
• 2 servings jjajangmyeon noodles (or kalguksu, udon, ramen noodles)
• Shredded green onions (optional), to garnish
• 2.5 tbsp fine Korean chili pepper flakes (or regular gochugaru)