Bring the butter, cream and brown sugar to a boil in a heavy saucepan. Boil for 5 minutes or until thickened and the sugar is dissolved, stirring often. Add vanilla. Pour carefull into a large bowl and add the sifted confectioners’ sugar immediately. Beat until creamy and smooth. Let the icing cool slightly.

Remove the cupcakes from the pan.The icing should still be warm but firm enough to just barely drip over the edges. Do a test on one cupcake and when it is the right consistency, go ahead and frost all the cupcakes fairly quickly before the icing hardens. (a small off-set spatula works well here) Sprinkle each with a healthy pinch of the flakey sea salt as you go so it will adhere to the wet icing. Let icing set before serving.