Yogurt with fresh blueberries on wooden background. Health concept.

When you think of yogurt, the words "sweet and fruity" might be the descriptors that come to mind. Omitted from that list is the word “sour,” which is a flavor not usually associated with yogurt – unless you’re wondering if your yogurt has gone bad – or if you’re planning to use yogurt as a substitute for sour cream.

As it turns out, making yogurt sour is a commonplace activity in many Indian restaurants and households. Only in that case, curd is yogurt, and it goes by the name "khatta dahi." It’s found in some of your favorite takeout faves, such as kadhi pakora, kadhi khichdi and mango lassi.

Making yogurt sour doesn’t require a wealth of Indian cooking knowledge. You can do it at home.

How to Make Curd (Yogurt) Sour

The process of turning curd sour involves the fermentation of milk and bacteria.

  1. To begin, bring 1 liter (a little more than 1 quart) of whole milk to a boil on low-medium heat (this helps kill the bacteria). 
  2. Let the milk cool slightly and pour it into the container that you plan to use for the yogurt. Let it cool at room temperature until it becomes lukewarm. 
  3. Next, add 3–4 teaspoons of the starter curd (yogurt) into the milk and stir it thoroughly.
  4. Cover the bowl and store it in a warm place, letting it set for 6 to 10 hours.
  5. Once the curd has set, place it in the refrigerator.

Don't use it for 1–2 hours or until it's chilled. It will last for four or five days.

A Quicker Way to Prepare Kadhi

Kadhi is a popular Indian dish that consists of pakoras – vegetable fritters made of chickpea flour – with dahi (sour yogurt) as the sauce base. You can serve it with roti, an Indian flatbread, or with rice. When served with rice, it's called khadi chawal.

Making kadhi at home requires a number of steps and ingredients. Many cooks turn to their Instant Pot to prepare this dish. You can make it "pot-in-pot," or PIP Instant Pot cooking, which saves time by cooking the rice and kadhi together.

Another quick way to prepare the dish is by following this recipe from the Saffron Trail. Using a pot over low-medium heat, start by whisking besan, or chickpea flour, into the prepared curd. Bring everything to a simmer and use enough water necessary to thin the mixture.

Many spices go into creating this flavorful dish, including curry leaves, cloves, garam masala and more (exact measurements can be found in any kadhi recipe). After adding in the spices, turn off the heat, but keep the pot covered so that all the flavors and infused into the dish. Serve with rice or roti.

The Two-Ingredient Recipe to Make Yogurt Sour Cream

If you're looking for a "lightened-up" version of sour cream, yogurt only needs lemons to get the job done. This quick recipe lets you enjoy that sour cream taste without all the extra calories.

All you need is 1 cup plain yogurt (Greek is a good choice if you like your sour cream thicker) and 1 tablespoon fresh lemon juice (about two wedges). Pour the lemon juice over the yogurt and stir.

Extra Add-Ins to Make Sour Yogurt Sweet

Eating sour yogurt all on its own can be difficult, so if you want to sweeten up the taste, you need a few add-ins. To reduce the tartness of sour yogurt, sugar is a good choice since the sweetness helps eliminate some of the tartness. Use plain sugar or opt for healthier options, such as maple syrup, fruit or fruit juice, liquid sweetener and flavor extracts.