Microwave the butter in a microwave-safe bowl for 15-30 seconds, until the butter is melted. Add 1/4 cup cocoa and blend until the cocoa is dissolved into the butter.
Add the sugar, milk and salt. Blend well.
Microwave on high for 1 minute 10 seconds to bring to a full boil. (Should you need to microwave the batter some more, do so in 10 second increments.) You want a full boil, but because it will continue to cook for awhile once it's removed from the microwave, heating it too long can cause the mixture to scorch.)
Add the vanilla, peanut butter and oatmeal. Stir well. Drop by tablespoon-full on waxed paper and allow to cool.
Makes 12 cookies.