Peel and grate the mangoes. Set aside

Heat the oil in a kadai or non-stick pan

Add the mustard seeds and fenugreek seeds, keeping heat low

When the mustard seeds pop, add the red chilli powder and turmeric

Give it a brisk stir and fry for 10 seconds, taking care not to burn the chilli powder. Keeping the flame low is important at this stage

Add the grated mangoes and mix everything well

Add salt and cook on medium-low flame until the mangoes let out water and soften

Add brown sugar or jaggery, if using

Continue cooking, stirring occasionally, until the oil separates from the thokku

Test to see there's enough salt and add more if needed

Remove from heat and cool completely

Store in a dry glass jar in the refrigerator for up to two weeks. Take care to use a dry spoon while