Take out a medium saucepan put on stove. Heat to medium heat. Add the butter to melt. Next, add the sugar and cocoa, mixing well. Add the milk. Let come to a mild boil and stir occassionally. This needs to boil for about 5 minutes or until mixture reaches soft ball stage. I judge this by stirring the mixture then holding the spoon up high and letting the mixture run off. When the drops start running together and slowly - it is done. Remove from heat. If you cook too much - your cookies will be dry and won't hold together. If you don't cook enough - they will be runny and you will have to eat them with a spoon. Add the oats, peanut butter and vanilla extract. Mix well then drop by spoon fulls onto wax paper to set up. Shouldn't take long. If cooked right - should only take about 2 to 3 minutes to set up.
They are delicious warm with a glass of cold milk. This recipe makes 1 & 1/2 to 2 dozen depends on how big you make them. I generally have to double this recipe if my sisters come over. No need to refrigerate - they won't last that long. They will keep in an air tight container for 3 to 4 days. Longer if you put in the refrigerator.
You can vary this recipe by adding your favorite ingredients. I have had friends use coconut instead of oats, add nuts, raisons or whatever they wanted to use.