Take 100 grams of walnuts and soak them in water for 30 minutes. After soaking, drain the water and set the walnuts aside.
In a pan, dry roast 1 teaspoon of cumin seeds and 1 teaspoon of coriander seeds until they release their aroma. Remove from heat and let them cool.
In a blender, add the soaked walnuts, roasted cumin and coriander seeds, 1 chopped green chili, 1 small piece of ginger, 2 cloves of garlic, a handful of fresh coriander leaves, a handful of fresh mint leaves, and salt to taste.
Blend the ingredients until you get a smooth paste. If needed, add a little water to adjust the consistency of the chutney.
Transfer the chutney to a bowl and add 1 tablespoon of lemon juice. Mix well.
For the tempering, heat 1 tablespoon of oil in a small pan. Add 1/2 teaspoon of mustard seeds and let them crackle. Then, add a pinch of asafoetida and a few curry leaves.
Pour the tempering over the chutney and mix well. Your walnut chutney is ready to be served.