Line an 8x4" loaf pan with parchment paper and line the bottom of the pan with graham crackers. Set aside.
Pour 2 oz. of the mini marshmallows out on to a baking sheet. Use a kitchen torch to toast the marshmallows, or place them under the broiler until toasted. Set aside.
Add the butter and salt to a large saucepan set over medium heat. Stir occasionally until the butter turns amber in color and develops little brown specks.
Add in the remaining 8 oz. of mini marshmallows and stir constantly until the marshmallows melt and the mixture is completely smooth.
Remove the mixture from the heat and mix in the vanilla, then mix in the Rice Krispie cereal.
Allow the mixture to cool for 5 minutes. In the meantime, chop up your chocolate baking bar.
Add the toasted marshmallows and chopped chocolate into the Rice Krispie mixture and do a couple of big folds to incorporate them into the mixture.
Pour the mixture into your prepared loaf pan. Use a spoon or flat spatula to lightly spread the Rice Krispies into an even layer. (Do NOT pack the Rice Krispies down!)
Press additional marshmallows and chocolate into the top of the Rice Krispies if desired and use a kitchen torch to toast the marshmallows.
Cover the Rice Krispies and allow them to set at room temperature for at least 1 hour before slicing. Enjoy!