Start by grating the carrots and pressing out as much liquid as possible before measuring.
Heat ghee or butter in a pan, then add the grated carrots. Cook them on medium heat for about 5-8 minutes until they soften and turn slightly darker in color.
Stir in the condensed milk, mix well, and cover the pan. Let it simmer on low heat for another 8-10 minutes until the carrots are tender and the mixture is creamy.
Add in the cinnamon and nutmeg, and cook for a couple of minutes to bring out their aroma.
Carefully slice each croissant down the middle, leaving one side intact so they hold together.
Spoon the warm gajar halwa into the croissants, then finish with a scoop of vanilla ice cream. Garnish with crushed nuts and serve immediately while still warm.