Crush the garlic cloves in a mortar and set aside.
Put a pan on medium-high heat with oil. When the oil is hot, add mustard seeds.
When they start to sizzle, add the grated ginger and crushed garlic. Fry for a few seconds and add mango pieces.
Add sugar, vinegar, salt and chilli flakes. Mix everything and let it cook on medium heat for about 15 minutes or until the mangoes are cooked.
With a potato masher mash the mangoes to obtain the right texture of Chutney.
Correct the salt and turn off the heat. Store it immediately in a pre-sterilized glass jar and seal with the lid tightly. Put the jar upside down and leave it there for 12 hours.
Once opened, store it in the fridge.