Cover a large cookie sheet with parchment or wax paper.
Melt the butter in a large sauce pan on low heat.
Add the sugar, salt and half the milk to the pan and bring to a rolling boil.
Boil, stirring constantly for 2 minutes.
Toss the cinnamon with the oats and set aside.
Remove pan from the heat and add half the oats, the peanut butter and vanilla extract.
Mix until combined well then add the remaining oats and milk. Mix until combined.
Using a teaspoon or a cookie dough scoop and drop the cookie dough onto the cookie sheet leaving about 2 inches between each cookie.
Slightly flatten each cookie with the back of the spoon or dough scoop.
Allow cookies to sit undisturbed for a few hours or refrigerate to harden faster.
If desired melt chocolate chips or candy melts in a zip lock bag, snip a small hole in a corner and drizzle over the set cookies. Allow the drizzled chocolate to harden before storing in an airtight container.