Is it permitted to prepare instant soup in a cup on Shabbat?

Hello, If all the ingredients of the soup have already undergone the cooking process, it is permitted to prepare it on Shabbat as usual. And if not all the ingredients have undergone the cooking process, according to Sephardi custom it is permitted to prepare it in a third vessel, or by pouring from a second vessel (as explained in Yabia Omer, part 7, Orach Chaim, siman 40, letters 3-5). Among many Ashkenazim, the custom is to be stringent and not prepare it even in a third vessel. 

With blessings, Hillel Meirs