1. Make the roux first. Melt butter in a skillet over low heat. Add flour until it forms clumps.
2. Gradually add the condensed milk and continue stirring until you the whole can is in gravy.
3. Add the sugar, salt, and cocoa and continue mixing. Slowly add cold water until you achieve the desired consistency.
4. Place warm biscuits on a plate. Ladle chocolate gravy over biscuits and add sliced butter.