You need to line a sheet pan with baking paper, or just spread baking paper on a straight surface. You will not have time to do it later as the cookies need to be scooped out as soon as possible.
Prepare your kitchen towels and mittens to handle the hot pot with the hot milk and sugar mixture. You also need to have something to place the hot pot on so that you don’t damage the working surface.
In a large mixing bowl combine oats, peanut butter, peanuts, and chocolate chunks (or chips). Mix to incorporate.
In a small / medium size saucepan combine butter, milk, sugars, salt, and vanilla and let all ingredients melt into a consistent mixture, don’t hurry with bringing up the heat!
As you see that your sugars dissolved and butter melted, slowly bring the mixture up to a rolling boil and continue boiling for exactly 2 minutes. After the 2 minutes are up, take the saucepan off the fire.
Pour the liquid into the oatmeal mix and stir until all chocolate has melted. When the dough is well combined and the chocolate is melted, grab a spoon (you can use an ice cream scooper for prettier shapes) and scoop the cookies out onto the parchment paper. Don’t lose time on this stage as it is best to scoop the cookies out before they harden!
Let your cookies cool for at least 30 minutes. You can place the cookies to the refrigerator to speed up the process! If your no bake chocolate cookies are still warm and soft after 30 minutes, leave them to cool for longer!
Interestingly, if it is raining outside, there are chances your cookies won’t harden as fast, because the water vapor in the air will moisturize the no bake cookies.