Start by melting the butter in a pot, on the stove, over medium heat.
Once the butter is melted, add in your marshmallows, creamy peanut butter, and vanilla extract, stirring until it all melts together.
When your mixture is smooth, remove it from the heat and pour in your Rice Krispie cereal. Stir until fully combined.
Then, transfer your mixture to a greased 8x8 baking dish and use a spatula to press the mixture down, ensuring that it is smooth and even on the top.
Next, prepare your chocolate; add your chocolate chips and coconut oil to a small bowl and microwave in 2-3, 30 second increments, until the chocolate is fully melted. Make sure to stir in between, so that the chocolate and coconut oil are fully combined. You can also do this over the stove, using the double-boiler method.
Finally, pour the melted chocolate on top of your rice crispy treats and topped with crushed peanuts, if desired.
Refrigerate for two hours, then once your treats have solidified, slice them into squares, and enjoy! Store any leftovers back in the fridge for up to one week.