In a small pan on low heat, gently toast the sesame seeds for 30-60 seconds until just fragrant. Place into a spice grinder or pestle and mash into a paste. *Amount of oils in the seeds can vary. It may look more like crushed seeds rather than a paste and that is ok.
In a large pot, melt butter and stir in vanilla, salt and sesame seed paste until well combined. Then add marshmallows and stir until melted and all ingredients are combined.
In a large bowl, stir together melted marshmallow mixture with rice cereal until well coated. Press into a 9x13in dish or something similar. Let rest and cool for about 20 minutes. Then cut and enjoy! Store in air tight container for a week.