Whisk corn starch, salt, cocoa, and brown sugar together in a small saucepan.
In a bowl combine milk and eggs and whisk to combine. Pour this into the saucepan and place over medium heat, whisking constantly until mixture comes to a boil.
Boil 1 minute and remove from heat. Stir in butter and vanilla extract. Serve warm or chill. To avoid pudding forming a skin on top as it cools, gently smooth a piece of plastic wrap over the surface of the pudding. Serve warm or chilled with a dallop of whipped cream and crunchy cookies.
Store refrigerated in an airtight container no more than a couple days.
Recipe by Jellibean Journals at https://jellibeanjournals.com/easy-homemade-dark-chocolate-pudding/