Instead of cooking down the milk, you can use 1 1/2 cups canned unsweetened evaporated milk. It saves you cleaning a pot and about some time, but the taste will never be as good as using fresh whole milk and reducing it and you don't get that nice crunchy caramelization. It's important that the carrots are coarsely grated, the halwa should have some texture and not be a total mash up.