Chop the mangoes with the skin into bite sized pieces and keep aside. Roast the fenugreek seeds until they turn dark brown and grind into a fine powder and keep aside. Add salt to taste, turmeric powder and chilli powder into the chopped mangoes and keep aside. Add powdered fenugreek seeds and asafoetida and season with mustard seeds. After the ingredients cool down to room temperature, mix well and serve.