Line a square baking pan with parchment paper. Set aside.
In a medium saucepan, melt the condensed milk. Once melted and liquidy, remove from heat.
Slowly sift the cocoa powder into the melted condensed milk, mixing until fully incorporated.
Using a rubber spatula, transfer the mixture into the prepared baking pan. Refrigerate for at least 2 hours.
Once refrigerated, using a cookie scoop, scoop the truffles into balls. Roll in additional cocoa powder. Store in an airtight container.