If you would like the preserve to be more like jam, then run the mango a couple of times in the blender.
Put all the ingredients, except the ginger in a microwave safe bowl. Mix and then cook at 100% for ten minutes.
Now add the ginger, stir well and microwave at 80% for another 8 minutes. Allow the preserve/ jam to cool. It will thicken a little bit.
Bottle and refrigerate. You might have to adjust your cooking time depending on the variety of mango.
Similarly, you might need to adjust the jaggery/ brown sugar required depending on the sweetness of your mangoes.