Kasundi — Fermented Mustard Sauce

Name: Kasundi — Fermented Mustard Sauce
Prep time: 30 min
Cook time: 10 min
Total time: 40 min
Yield: 12 servings
Cuisine: Bengali
Ingredients: 150 g black mustard seeds; 50 g yellow mustard seeds; 50 g Green mango; 6 piece green chilli; 5 g turmeric powder; 80 ml mustard oil; 20 ml Vinegar; 15 g Salt

A sharp, tangy fermented mustard sauce used across Bengal as a dip for fried fish and vegetables, made traditionally with sun-fermentation.

🇮🇳India· West Bengal

Prep: 30 min
Cook: 10 min
Total: 40 min
Servings: 12
Difficulty: Medium
Calories: 45 kcal

Ingredients

0 of 8 gathered

Servings

Equipment

•Grinding stone or blender
•Sterilised glass jar

Nutrition

Per serving, approximate

Calories: 45 kcal
fat: 4 g
carbs: 2 g
fibre: 1 g
protein: 1 g
calories: 45 kcal

Instructions

1
Grind the soaked black and yellow mustard seeds, green chillies, turmeric, and a little water into a smooth, thick paste.
2
Stir in the chopped raw green mango, if using, along with the salt.
3
Spoon the paste into a clean, dry glass jar. Pour the mustard oil generously over the top to cover it completely.
4
Cover the jar with a breathable cloth and tie it securely. Do not use an airtight lid.
5
Leave the jar in direct sunlight for 3–4 days. Stir daily with a dry spoon and top with oil each time.
6
After fermentation, stir in the vinegar, if using, to help preserve the sauce.
7
Move to a clean, airtight jar once fermentation is complete and a sharp, tangy aroma develops.
8
Store the jar in a cool place, or refrigerate it to keep it fresh longer.

Chef's tips

Always use a completely dry spoon when handling kasundi (fermented mustard sauce) to prevent spoilage. Do not skip the sun-fermentation step, as it creates the signature pungent tang.

Ingredient substitutions

green mango → a splash of extra vinegar for tang if unavailable

Storage

Refrigerate in an airtight jar for up to 3 months after fermentation is complete.

Reheating

Not applicable — served cold or at room temperature.

Common mistakes to avoid

•Using a wet spoon, which introduces moisture and quickly spoils the batch.
•Sealing the jar with a tight lid during fermentation, which traps gases and stops proper fermentation.