Preheat the oven to 180°C. Grease and line a 9 inch square tin.
Add the sugars to a freestanding mixer with the butter. Beat until well combined and a little fluffy. Add in your egg, mix until it’s incorporated.
Scrape down the sides of your bowl, gently mix through the flour and salt, followed closely by the chocolate. Pop this into the tin and press to create a smooth, even surface, I like to use the back of a spoon for this.
Pop it in the oven for 15 minutes until it’s risen a bit and golden in colour, it will still be a little wobbly. Don’t forget; it will continue to cook in the tin.
To make the crispy top: Melt the Mars Bars and butter in a large saucepan over low heat, then stir through the Rice Krunchies. Pop this on top of the cooled cookie base, pressing it in a little.
For the topping, melt the chocolate with the sunflower oil in a bowl set over a saucepan of simmering water.
Pour the melted chocolate over the crispy layer, sprinkle with the Mini Eggs and then refrigerate for at least an hour until it’s all set.