Prepare a pan by lining it with foil and spray with cooking spray.

In a medium pan over medium-low heat, add butter. Once the butter melts, add marshmallows and stir until it completely melts.

Quickly remove from heat and add vanilla extract.

At this stage, add fruity pebble cereals and stir gently to coat with marshmallow mixture.

Then transfer the mixture to the prepared pan and press strongly to compact with the help of wax paper sprayed with cooking spray.

Leave to rest until firm, then slice into bars and serve. You can also store it in an airtight container for future use.