Add the mango puree to a heavy bottom saucepan and bring it to boil on medium heat.
Keep stirring constantly till the mixture thickens and becomes half in volume. It will take around 10-15 minutes.
Set aside to cool.
Make the cookies
Preheat your oven to 175C, prepare a cookie sheet.
In a bowl add the butter and sugar, whisk very well for 2 minutes using a whisk.
Now add the cooled mango puree reduction and vanilla, mix until combined. You can also add up to 2 drops of yellow food colour for a brighter yellow coloured cookie.
Sift the all-purpose flour, baking soda, baking powder and cornflour into this bowl and mix until you don't see any dry flour.
The dough should be scoopable and not too loose. If it is very runny, refrigerate for 30-45 minutes so you can scoop it out. The dough should not be too dry or too hard.
Scoop the cookie dough and roll it in regular granulated sugar crystals and place on a prepared cookie sheet lined with parchment paper.
Place them a little apart from each other because they will spread a little. (If they do not spread, please check notes and FAQs above the recipe card). You can press down the cookie a little to help it spread but if you face issues, please read the questions above the recipe card.
Bake the cookies at 175C for 12-16 minutes depending on your preference of texture. If you bake them longer they will become more crispy.
Let the cookies cool on the tray for 10 minutes before consuming. The cookies become firmer as they cool down.