Combine the butter, sugar, milk, and cocoa powder together in a medium saucepan (about 3 quart) over medium heat. Whisk constantly until the butter melts. Whisking occasionally, bring to a boil. Once boiling, stop whisking and allow to boil for 1 minute. Remove from heat, then immediately stir in the peanut butter and vanilla extract until completely combined. Stir in the oats and salt. Allow mixture to sit for 5 minutes. This allows the oats to soak up some moisture. During the 5 minutes, line two baking sheets with parchment paper or silicone baking mats. And make sure there is enough room in your refrigerator for the baking sheets. Using a 1-Tablespoon cookie scoop (or simply a spoon), drop a Tablespoon of dough onto the lined baking sheets. If desired, slightly flatten down with the back of a spoon. Repeat with the rest of the dough.