Sweet Potato & Ginger Soup (姜汁番薯糖水): A Warm, Simple Tong Sui

After a run of chilled summer soups, here's one to reach for when you want something warm — soft chunks of sweet potato in a light, fragrant ginger syrup. Sweet potato and ginger soup (姜汁番薯糖水) is one of the simplest sweet soups in the whole repertoire: three main ingredients, one pot, and about half an hour. It's the kind of humble, comforting bowl that turns up on cooler evenings, and it's a lovely, gentle introduction to cooking tong sui.

The magic here is the pairing — the mellow, honeyed softness of sweet potato against the warm bite of ginger, tied together with just enough rock sugar. Nothing fancy, and all the better for it.

Just three things to get right

This soup is almost impossible to mess up, but a few small choices make it better:

• Pick a good sweet potato. The orange-fleshed kind gives a sweeter, creamier soup; yellow-fleshed ones are firmer and less sweet. Either works — just know what you're getting.
• Use plenty of ginger, sliced. Fresh ginger is the whole character of this soup. Slice it thin (peeling optional) so it releases its flavor into the syrup as it simmers. More ginger, more warmth.
• Don't overcook the sweet potato. You want the chunks soft but still holding their shape, not collapsed into mush. Add them once the ginger syrup is going, and check with a chopstick.

Ingredients

Makes about 4 servings

• 2 medium sweet potatoes (番薯), about 500g
• A generous thumb of fresh ginger (姜), about 30–40g, thinly sliced
• 50–70g rock sugar (冰糖), to taste (brown sugar or 片糖 also works, for a deeper flavor)
• About 1.2–1.5 liters (5–6 cups) water

How to make it

1. Prep. Peel the sweet potatoes and cut them into bite-sized chunks. Slice the ginger thinly.

2. Start the ginger syrup. Add the ginger, rock sugar, and water to a pot. Bring to a boil, then simmer for about 10 minutes to let the ginger infuse the water.

3. Add the sweet potato. Add the sweet potato chunks and simmer gently for about 15–20 minutes, until they're soft enough to pierce easily with a chopstick but still holding their shape.

4. Taste and serve. Adjust the sugar to taste. Serve warm, with a few slices of ginger in each bowl. It's a warming soup at heart — best enjoyed hot.

Tips

• Try it with brown sugar or 片糖 (slab sugar). For a deeper, more caramel-like syrup, swap some or all of the rock sugar. It's a common variation and very good.
• Adjust the ginger to taste. Start with less if you're ginger-shy, more if you love the warmth. You can always simmer a bit longer for a stronger kick.
• Add a few small tang yuan. For a heartier bowl, drop in some small glutinous rice balls in the last few minutes — a classic addition, especially in winter.
• Keeps well. It reheats beautifully, and the ginger flavor deepens overnight.

Building your sweet soup pantry

Rock sugar and fresh ginger are worth keeping on hand for sweet soups year-round. The dried staples for the rest of the recipes here are on the Pantry page.

If you liked this warm, simple bowl, you might enjoy the cozy black sesame soup next. For something lighter, there's the red date and longan tea.

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