Slice the potatoes as thinly as possible to shorten cooking time.
Julienne the onion, put it in a pot, and stir-fry vigorously until it turns brown (caramelized) and starts to smoke.
Add 2 cups of water to the caramelized onions, then add all the sliced potatoes.
Cover the pot tightly and boil on high heat for about 15 minutes until the potatoes are completely mashed, creating an onion-potato soup base.
When the potatoes are cooked, reduce the heat, pour in the milk, and before it foams up and boils over, blend smoothly with a hand blender.
Simmer the blended soup for about 10 more minutes until thickened, then season with salt, pepper, and chicken stock to taste.
Serve generously in a bowl and top with corn flakes for a classic Western-style diner feel.
Add water to thinly sliced potatoes and stir-fried onions, cover, and boil for 15 minutes.
Pour in milk, blend smoothly with a hand blender, then simmer on low heat for 10 more minutes.
Season with salt, pepper, and chicken stock, then top with corn flakes and serve.
Cooking tips 💡
If you boil milk from the start, it easily foams up and overflows everywhere, so it's more convenient to first cook the potatoes with water, then add the milk.
Adding a little chicken stock adds a deep, rich umami flavor reminiscent of restaurant-style soup.