Combine the whites, powdered sugar, and salt in the bowl of a large stand mixer. Mix well. Turn off the mixer, scrape down the sides and bottom of the bowl with a spatula, then turn the mixer to medium speed. Beat on medium for 5 minutes. After 5 minutes, turn the mixer to medium-low and start adding the softened room temperature butter, 1-2 tablespoons at a time. Once all of the butter is incorporated, add the cardamom powder, rose water and saffron and mix it in. After a min or so scrape down sides once more. Turn the speed to medium and beat the buttercream for 10 minutes. At the end, you’ll have a frosting with a wonderfully light and creamy texture. Set your cupcakes on a flat surface and scoop out the inside a little, about the size of a quarter. Now cut a rasmalai in half and stuff it and put 2 tsp of the rasmalai milk on it cover it with the part of the cupcake you scooped out. Now put your icing in a bag and cover your cupcake ( I use a large wide star tip ) now put the other 1/2 of the rasmalai on the top securing it in the frosting top with above garnishes as desired.