Grate it using a box grater or food processor .Make it thicker if you like the chutney chunky.
Heat a pan with the Mustard Oil. Let it smoke. Lower the heat after.
Add the cumin or kalonji and Red chili. Let the cumin splutter
Add the grated Mango, Sugar,Salt and Water.
Let it cook open for 15-20 minutes on low heat.
Once all the mango slivers look translucent and mushy, you can switch off the heat.
Let the chutney come to room temperature before storing.
Video
Notes
500 gms of Whole Raw Mango is about 3 Cups of Grated Mango.Add more Sugar if the Mangoes are very sour.StorageStore the chutney in an clean air tight jar for upto 3-4 weeks