In a pan add little oil and let it heat a bit.
Now add asafoetida, cumin seeds, nigella seeds, carom seeds, fenugreek seeds, fennel seeds & dry red chillies.
Mix and let it roast for a while on low flame.
After 1 minutes add mangoes and cook for a while.
After its cooked a bit add water increase heat to medium.
Add salt cover and cook for 7-8 minutes or till mangoes are cooked while stirring in between.
Once mango is cooked add jaggery, red chilli, garam masala powder, chaat masala and black salt.
Cook till jaggery thickness a little once thick turn off the heat.
Let it cool down completely before storing in clean, dry glass container.