Preheat the oven at 350F.
In a spice grinder add castor sugar, and pulse until powdered.
Sift and add the powdered sugar to a mixing bowl.
To this, add ghee, tahini, cardamom powder, and baking soda.
Whisk it until fluffy.
Now sift in the all-purpose flour and besan.
Using a spatula, fold the ingredients together to make the dough. Don't knead the dough.
The dough should come together easily.
If you think your dough is very soft, cover it with a plastic wrap and keep it in the refrigerator for 20 minutes.
Then using a cookie scoop, make equal parts of the cookie dough. Roll them round, and flatten them just a little bit between your palms.
Now roll the prepared cookie dough balls in the sesame seeds.
Now place the cookie dough balls, on a parchment lined baking tray.
Bake the Tahini Nankhatais for 12-15 minutes. Baking time depends on your oven. Keep an eye on them from 10 minute mark.
Take them out of the oven. Transfer them immediately on a wire rack and and let them cool.
Serve them with masala chai or coffee.