First, peel the carrots and cut them in big chunks and slice them in half vertically . If the carrots have thick yellow center, remove it and discard.
In the Instant pot, add chopped carrots, 1 cup milk, ½ cup heavy cream and 1½ cup sugar. Mix everything.
Close the lid and pressure cook for 12 minutes. Make sure instant pot is in sealing. After 12 minutes press cancel and let the pressure release naturally for 2 minutes and then do a quick pressure release by moving the pressure valve from sealing to venting position.
Open the lid and give everything a mix. The halwa will look very watery at this stage. Switch on the saute mode and mash the carrots with a potato masher. Keep mashing and stirring till the liquid is absorbed and the carrots are completely mashed.
Once the liquid is absorbed, press cancel.
Heat ¼ cup ghee in a wide non stick wok/kadhai. Fry sliced almonds and raisins(kishmish) for few seconds until almonds are golden. Next, add mashed carrots and mix in the ghee and nuts. Fry for 2-3 minutes.
Add mawa and check if more sugar is required . Add ¼ cup sugar if required and at this stage you can add ½ tsp of red food color if your carrots are orange. This step is completely optional and it is just to give the halwa a traditional red color.
Add 1/2 tsp of cardamom powder and a pinch of nutmeg. You can also add 1 tbsp ghee at this stage for richer flavor. Switch off the flame.
Garnish with more nuts and serve warm.