Rinse the rice gently under cold water until the rinse water runs mostly clear (about 3–4 rinses). This removes excess surface starch so the grains don’t gum up while simmering; we want a creamy, separate-grain congee rather than a gluey paste.

Combine the rinsed rice and 750 ml water or low-sodium chicken stock in a medium heavy-bottomed pot. Add the julienned ginger (reserve a few matchsticks for garnish) and bring to a gentle boil over medium-high heat. Using stock adds extra savory depth (umami), while water keeps the flavor neutral—choose based on how savory you want the final bowl.

Once it reaches a boil, stir once to release any rice that’s stuck and lower the heat to maintain a bare simmer (small bubbles breaking at the surface). Partially cover the pot with the lid tilted to allow steam to escape. Cook at this gentle simmer for 35–45 minutes, stirring every 6–8 minutes and scraping the bottom of the pot with a wooden spoon to prevent sticking. Slow simmering breaks the rice grains down into a silky porridge; stirring periodically helps the grains release starch and prevents scorching.

Check texture at 30 minutes: the congee should be thick but spoonable and the rice grains should be breaking apart into threads. If it’s too thick for your taste, add a few tablespoons of hot water or stock. Adjust seasoning with 1/4–1/2 tsp salt (taste and add more if needed). Seasoning early allows the rice to absorb salt evenly; you can always adjust further at the end.

While the congee finishes, poach the egg: bring a small saucepan of water to a gentle simmer (not a rolling boil) and add a teaspoon of white vinegar if you like crisper white edges (optional). Crack the cold egg into a small cup. Create a gentle whirlpool in the water with a spoon and slip the egg into the center; cook 3 minutes for a soft, runny yolk and just-set white. The whirlpool helps the egg white wrap around the yolk for a neat, restaurant-style poach. Remove with a slotted spoon and briefly rest on a paper towel.

Taste the congee and finish with the 1 tsp sesame oil, a few grinds of cracked white pepper, and more salt if needed. The sesame oil is added right at the end to preserve its nutty aroma; cooking sesame oil breaks down its fragrance.

Ladle the congee into a warmed bowl. Gently place the soft-poached egg in the center. Top with the thinly sliced scallion, 1 tbsp quick-pickled mustard greens, reserved ginger matchsticks, a light crack of white pepper, and a cilantro sprig. The pickled mustard greens add a sharp, salty contrast and crunchy texture that elevates the smoothness of the congee.

To serve: break the egg so the runny yolk ribbons into the congee, stir gently and taste for salt and pepper one last time. Serve immediately while steaming hot.