In a large pot, melt one stick of butter over medium heat.
While the butter is melting, lay out a piece of wax paper (about 2 feet long) along the counter.
Once the entire stick of butter has melted - add milk, sugar, and cocoa powder. Increase heat to medium-high.
Once the mixture starts to boil (full boil - not just a few bubbles), set timer for 2 minutes. Do not stir while boiling.
After the 2 minute boil, remove from heat and add 1 tsp of Vanilla (stir) and 2½ cups of oatmeal. Mix well.
If you are using peanut butter, you will add it after the vanilla.
Drop the mixture by spoonfuls onto wax paper.
(I use a cookie dough scoop and then "squish" them down with the round part of the scoop so the cookies aren't too mounded up).
Let cool until cookies are firm (usually 15-20 minutes).
Lift up the wax paper off the counter to test if the cookies are set.