Line a 9x9inch square tray with parchment paper and leave to the side.
Add the unsalted butter to a large pan and heat on a low heat, stirring frequently, until the butter has melted.
Add in the white mini marshmallows and continue to heat on a low heat stir frequently. At first it may look lumpy, but after a while, and a bit of beating it’ll be smooth and pourable.
Pour in your Rice Krispies and mix together until all of the Rice Krispies are covered evenly – this can take a bit of welly but its worth it!
Press down into your tray evenly (the mixture is very sticky, so you may want to use gloves, or the back of a spatula, but I find rubbing my hands in butter so it doesn't stick and using my hands is easiest!) and leave to set – this can take 2+ hours.
Caramel
In a medium saucepan pour the condensed milk, unsalted butter, caster sugar, and golden syrup and melt on a medium heat till the caster sugar has dissolved – stir frequently to stop anything from catching.
Once the sugar has dissolved, turn the heat up high and let the mixture come to boiling point and boil for 5-7 minutes stiring constantly so that the mixture doesn’t catch.
BE CAREFUL as the mixture is VERY hot and can burn you if it splashes back! The mixture will be ready when it has changed to a slightly darker golden colour, and has thickened to a soft fudge texture!
Pour the caramel on top of the marshmallow Rice Krispie layer and chill in the fridge.
Topping
Once chilled, melt the chocolates and pour over the caramel.
Swirl them together with the end of a skewer so it forms a pretty pattern. Leave to set!
Chop up your Millionaires Rice Krispie Treats into the separate pieces and enjoy!
Notes
If you struggle to cut your tray bakes without the chocolate cracking on top, set it at room temperature rather than in the fridge and it’ll be softer so therefore won’t crack when you cut it! You can then put it in the fridge after to continue firming up, or keep it at room temperature if you prefer everything slightly less chewy.
Alternatively, you can warm up a large sharp knife and use this to cut your treats.
If your caramel is rock solid when you remove it from the fridge, you have slightly over done it. Not to worry though, when you pour the chocolate on, leave it to set at room temperature rather than in the fridge and it should soften the caramel slightly.
These will keep in an airtight container for at least 1 week – if they last that long!