In a large sauce pan over medium heat, bring sugar, butter, milk and cocoa to a boil stirring occasionally. Stir constantly for one additional minute and remove from heat.
Add vanilla, oats and chocolate chips. Stir until combined.
Let the mixture cool for 15 -20 minutes. This will firm it up enough so cookies will hold shape when you scoop them out. Use a 1oz cookie scoop to drop unto wax paper. Alternately (for easier transportation) drop cookies into paper muffin liners and use to serve.
When cookies have set, remove from paper and store in an airtight container. These can be stored for a longer time in the freezer.
Cooking the cookies: 10 minutes. Waiting for batter to cool: 20 minutes. Scooping them out: 10 minutes. Time for cookies to set: 1-2 hours.