Preheat the oven: preheat the oven to 180°C / 350-375°F / Gas Mark 4-5.
Slice tray: line a 9 x 13 inch (33cm x 23cm) slice tray with 2 sheets of overlapping baking paper with a 1-2 inch over hang on each side. Note 4
Toffee layer
Butter and sugar: add both the butter and sugar to a heavy based sauce pan. Allow to melt using medium low heat. Stir to combine as it melts. Once the butter is melted and you start to see one color in the pan and not 2 separate colors watch the bubbles. When you see the bubbles make their way from the centre to the outside of the sugar mixture stop stirring and allow to bubble away for 30 seconds. After that, remove from the stove top, give a gentle stir and then pour over the biscuit layer.
Oven bake: spread the toffee out so that it completely covers the biscuits then place this into the oven and let it bake for 8 minutes. (The toffee layer will be bubbling away, this is to be expected).
With 3 minutes to go ie after baking for 5 minutes start melting the chocolate as per the step below.
Chocolate layer
Chocolate: add the chocolate to a heatproof jug. Microwave in 1 minute increments on high for a total of 3 minutes.
Combine: use baking mitts to remove the slice tray from the oven at the 8 minute mark and set it onto a heatproof surface. Pour the melted chocolate over the top and then use a spatula to spread it out across the toffee layer.
Decorate
Sprinkles: sprinkle the colored hundreds and thousands across the white chocolate layer.
Set
Refrigerate: place in the fridge until the chocolate has set and the toffee has hardened. Then break into pieces and serve.
Video
Notes
Note 1 - Salada biscuits or saltine crackers: these biscuits come as a square comprised of 4 smaller squares. The recipe needs 6 'original squares' or 24 small biscuit squares. See the photo where I am laying the biscuits into the tin if unsure.
Note 2 - White chocolate: I use 2 blocks (200 grams each ) of white cooking chocolate. In the testing process I used 1 bag of chocolate chips but I found that this was not enough, you need more to create a good solid chocolate layer. Also cooking chocolate is always best and recommended for baking/making/melting not regular eating chocolate.
Note 3 - Sprinkles: you don't have to use the exact same type and color of sprinkles that I am using. Feel free to use your favorite combination and decorate to occasion. Be it festive for Christmas, pink for Valentines or how ever you want to decorate it. M and m's, crushed candy canes, sprinkles, cachous, lollies, biscuit pieces etc etc.