If you loved a rice crispy treat/cake in your childhood, you'll love this. Except this version, is a little more grown up. It's still chewy and moorish but has a pop of lemon juice and zest to offset the sweetness.
Melt the butter and marshmallows in a frying pan over a low medium heat. Stir until fully melted and smooth.
Add the lemon juice, zest, vanilla extract, poppy seeds and a pinch of salt to the mixture and stir to incorporate.
Add the still warm marshmallow mixture a large bowl with the rice krispies. Once fully incorporated tip into a lined square dish or baking tray. Zest over some more lemon, then press firmly with some baking paper to flatten and get an even surface.
Place in the fridge to firm up then slice into bars and enjoy or store in a airtight container for a few days.