Instructions

1. Prepare a 23cm square slice pan by lining it with baking paper. I like to spray a little cooking spray on the pan before the paper to help it stick to the pan. Ensure at least two sides come above the top of the pan, to make lifting the slice out easier later on.
2. You can melt the first three ingredients in the microwave or on the stove top.
3. In a microwave proof bowl OR saucepan, add the first measure of butter, condensed milk and sift in the cocoa powder
4. Heat in microwave in 30 second bursts until the butter is melted, OR on the stovetop on a medium/low heat until the butter is melted. Stirring often.
5. Crush the biscuits in a food processor or blender and add the crushed biscuits along with the cornflakes (OR coconut if using) to the melted ingredients and stir well to combine. Give the cornflakes a little smash as you mix them through!
6. Spoon this into the prepared pan and spread evenly to the edges. Use the base of a 1/3rd measuring cup to ensure the slice is well compacted, smooth & even.
7. Pop this in the fridge to cool while you prepare the filling
8. For the filling, bring a kettle of water to the boil.
9. Melt the butter in 20-30 second bursts in a small bowl in the microwave until completely melted, add the peppermint essence to this and set aside.
10. In a medium bowl sift in the icing sugar, add to this the melted butter & essence and mix with a wooden spoon or strong spatula to combine well
11. To this add 3 Tablespoons of boiling water and stir together well. Then add a further tablespoon of boiling water and mix well ensuring no lumps.
12. Add a teaspoon at a time of boiling water until you are happy that the consistency is thick but just soft enough to spread smoothly.
13. Pour this over the sightly cooled base, then using a large spoon or an offset spatula dipped in hot water, spread the filling until it is an even smooth layer.
14. Place this in the fridge for 20 minutes to begin to set, while you prepare the chocolate.
15. Place the dark chocolate in a small microwave safe bowl, melt the chocolate in 20 second bursts, until only a few small lumps remain, then mix those in well until smooth. Use 70% power if your microwave high powered.
16. Add to this 1/2 teaspoon of oil and mix through well and set aside
17. If using, place the white chocolate in a small bowl, and heat in 10-20 second bursts until only a few lumps remain then mix them in. Then add a little dash of oil and stir well.
18. If you are using the white chocolate to create a pattern, add the white chocolate to a small ziplock bag and get a toothpick or kebab stick.
19. Spread the dark chocolate over the cooled filling, working quickly. Use the back of a large spoon or an offset spatula to ensure the chocolate is smooth. Then give the whole dish a jiggle to settle the chocolate evenly.
20. To create the pretty white chocolate pattern, cut a tiny corner of the ziplock bag off, and squeeze gently to draw lines of chocolate 1 cm apart in one direction.
21. Then take your skewer and drag a line up through the lines you have just drawn, and then one down in the opposite direction, 1 cm apart and repeat across the slice.
22. Give the slice a gentle jiggle to settle the chocolate to a lovely smooth layer and pop it in the fridge to set, approx 2-3 hours.
23. Once set, remove from the tin using the baking paper to lift the slice.
24. To cut, dip a large sharp knife in hot water, dry it off, then cut the slice in half, dipping and drying the knife between each cut.
25. Then cut each half into quarters, then cut each segment into squares or bars.
26. Store at room temperature in an airtight container for 4-5 days, or wrap well in plastic wrap then an airtight container to freeze for up to 3 months.
27. Enjoy!