Preheat oven: to 180°C / 350-375°F / Gas Mark 4-5.
Baking dish: line a 9 x 13 inch (33cm x 23cm) with 2 sheets of overlapping baking paper with a 1-2 inch over hang on each side. Note 4
Biscuit layer: place the salada biscuits into the prepared slice tray in one flat layer.
Toffee layer: add both the butter and brown sugar to a heavy based sauce pan. Turn the heat to medium low. Stir occasionally as it melts. When you see one colour (light brown) instead of 2 (yellow and brown) in the pan, let the bubbles go from the centre all the way out to the edges. When the bubbles are at the edges of the pan let it bubble for 30 seconds without stirring.
Combine: remove the pan from the stove top, give it a quick stir and then pour the combined toffee over the biscuit layer.
Oven bake: now place the slice tin into the oven (uncovered, middle shelf) and let it bake for 8 minutes.
Microwave: in the final 3 minutes of the oven bake time above put the chocolate into the microwave and melt in 1 minute increments for a total of 3 minutes. Note 5
Combine: use oven mitts to remove the slice tray from the oven and set it on a heat proof surface. Pour the melted chocolate over the top and use a spatula to spread it out in one layer.
Decorate: spread the mini m and m's across the melted chocolate and then use the sprinkles on top as a finishing touch.
Set: place the decorated salada crack into the fridge to set. (3-4) hours. Once set break apart into pieces and serve.