Combine sugar, salt, evaporated milk, and butter into heavy duty sauce pan

Working very fast pour 1/2 cup of mixture into a glass measuring cup. Add white chocolates, do not store, just set aside.

Working fast stir remaining chocolate into pan mixture, until just melted, then pour into lined pan.

Stir white chocolates until just melted. Drizzle into chocolate in pan, swirl with a spoon, refrigerate 2 hrs, remove from pan, take liner off, cut into pieces.