Heat the oil in a 5 quart pot over medium high to high heat; add half the steak in an even layer on the bottom and cook until browned. Use a slotted spoon to transfer the browned steak to a bowl; cook the remaining steak the same way and transfer it to the bowl.: Right away you will notice the satisfying sizzle as the surface of the skirt steak hits the hot oil, releasing a nutty, roasted aroma and producing a deep brown crust that smells almost sweet and savory at once. The sizzling sound is your cue that the pan is hot enough to create fond, the browned bits that stick to the bottom and will later flavor the broth. Work in batches to avoid crowding, because when meat is crowded the pan temperature drops and the steak steams instead of browns, leading to gray, flabby pieces rather than flavorful, caramelized edges. As you transfer the seared steak with a slotted spoon, you will see juices collect in the bowl, which is normal; these concentrated juices matter for texture and mouthfeel. One common misstep here is cooking the steak too long; since the slices are thin, they only need a short time to develop color and can become tough if overcooked. Resting the seared steak briefly in the bowl allows carryover heat to finish it without drying the meat, and saves the fond for the next step.
To the pot that you cooked the steak in, add the bell peppers and onion; cover the pot and cook over medium heat until the vegetables start to soften, about 4 minutes, stirring occasionally. Add the garlic and ginger and cook 1 minute more, stirring constantly.: As the bell peppers and onion meet the hot pan, they will hiss and release a sweet, vegetal aroma; cover the pot to trap steam and coax them to become tender while still retaining some texture. Stirring occasionally prevents uneven browning and helps the vegetables sweat, drawing out natural sugars that add depth to the broth. When you add the crushed garlic and grated ginger , the scent will brighten, producing a peppery and aromatic perfume that fills the kitchen, but keep stirring to prevent burning which can introduce bitter notes. The one trap here is rushing the heat too high to speed things up, which can char tiny bits of garlic and impart a charred taste. Gentle medium heat for the short time specified lets the aromatics bloom, laying a flavorful foundation for the liquid to come.
Stir in the broth, soy sauce, rice vinegar, sugar, fish sauce, coriander, crushed red pepper flakes, turmeric, salt, and black pepper. Bring to a boil, and then cover the pot, turn the heat down to simmer, and cook 5 to 10 minutes. Add the cooked beef back to the pot.: When you add the beef broth and the seasoning ensemble, the pot will immediately steam and the kitchen will get a complex fragrance, with savory, tangy, and sweet notes mingling. Bring it to a boil to quickly marry the flavors and then reduce to a gentle simmer so the ingredients can meld without aggressive evaporation. The simmer time softens the peppers and onions and allows the powdered coriander and optional turmeric to release subtle background flavors, while the fish sauce and soy deepen umami. Return the seared skirt steak to the pot toward the end of the simmer so it warms through without overcooking; this keeps the beef tender. A common error is simmering too rapidly or too long which can evaporate flavors and toughen the meat, so aim for a steady, low simmer for the time suggested.
Stir in the coconut milk and cilantro or parsley and turn off the heat; taste and add additional salt as desired.: As you pour in the can of full fat coconut milk , you will see the broth transform to a creamy, opaque finish that softens the spices and offers a luscious, velvety mouthfeel. Swirling in chopped cilantro or parsley at this stage introduces a green, herbaceous note that lifts the richness. Turn the heat off to keep the herbs vibrant and avoid breaking the coconut fat with prolonged boiling. Taste carefully for salt because the combined impact of soy , fish sauce , and the broth can vary; adding salt at the end lets you tailor the bowl to your palate. Over seasoning early is a typical mistake, so adjust gradually and taste between additions to avoid an overly salty final soup.
Serve garnished with suggestions above anything you like!: When you ladle the soup into bowls, notice how the steam rises, carrying the fragrant mix of ginger , garlic , and coconut, and how the beef pieces float warmly in the creamy broth alongside colorful bell peppers . Garnish with extra fresh chopped herbs or a sprinkle of crushed red pepper flakes to add visual contrast and a final kick. Serving hot preserves the silky texture of the coconut and the tenderness of the steak, while allowing guests to add extra heat or herbs at the table. A frequent serving mistake is letting the soup sit too long before plating, which dulls aromas and cools the coconut fat, so serve immediately for the best sensory impact.