The recipe calls for 1 1/2 cups of superfine sugar, but ends up using only 1 cup in the method. (epicurious.com)
First I would invest in superfine brown rice flour instead of just plain brown rice flour. (cannellevanille.com)
I heated the evaporated milk, melted the chocolate and whisked in all the listed ingredients, with about 1/8 cup superfine sugar added in as well. (epicurious.com)