Line a square tin (24cm x 5cm, 9" x 2") with baking/parchment paper, leaving a 1-2cm overhang on all 4 sides. Note 10
Make the coffee by adding boiling water to it, stir to dissolved, then set aside.
Add biscuits to the food process and blitz for 20 to 30 seconds till they are a fine crumb. Note 11
Add sweetened condensed milk and butter to a heat proof jug. Melt in the microwave for 2 minutes. Use a mini whisk to stir till consistently combined. Note 12
Add the butter mixture and coffee to the biscuit crumb. Use clean, dry hands to mix and knead this till combined.
Transfer the biscuit base into the lined slice tin. Use a spatula to spread it around and then a flat based glass to push firmly down. Note 13
Place the biscuit base into the fridge for approximately 30 mins.
Add the caramilk chocolate and olive oil to one heatproof jug and the white chocolate and olive oil to another. Microwave for 2 mins. Then stir to combine (separately, don't combine the 2 colours at this point).
Remove the biscuit base from the fridge. Pour the melted caramilk chocolate over the biscuit base, pick up the tin and move it around in your hands to get the chocolate to spread. Put it down again, then tap it gently a couple of times to remove any bubbles.
Use a teaspoon to spoon in a little of the melted white chocolate. Use a skewer to swirl this around the caramilk layer reminiscent of the top of a latte. Place the slice into the fridge for 2 hours to set.
Remove the slice from the fridge, give it 5 mins, then pull the sides of the baking paper up and out. Remove the paper and discard.
Use a sharp knife and chopping board and cut into pieces. Note 14