In a medium saucepan bring the butter, milk and sugar to a boil.
When the mixture begins to boil and you can’t break the boil by stirring it, set a timer for 2 minutes.
After 2 minutes of boiling, immediately remove from heat.
Stir the peanut butter into the saucepan until it is smooth.
Add the instant pudding mix and stir until smooth and no lumps of pudding remain.
Add 3 cups of oats and stir until well mixed. If the batter seems thin, add the remaining ½ cup of oats and stir well.
Set a timer for 4 minutes, and let the cookie mixture rest.
Line the countertop with parchment paper, or foil.
Drop the cookies by the spoonful onto the parchment paper and allow them to cool and dry for about 30 minutes before eating.
Store the cookies in an airtight container for up to 5 days.