Line a 8 inch cake tine with parchment paper leaving sufficient up the sides of the tin so you can lift out the slice.
Place the biscuits into a food processor and pulse to a medium crumb. Add the melted butter, golden syrup and coconut and pulse until well combined.
Press the mixture firmly into the pre-lined baking tin. Sprinkle the chopped walnuts evenly over the top of the biscuit base and place in the refrigerator to set.
Fudge
Place all the ingredients, except the Butterscotch vanilla extract, into a medium sized, heavy based saucepan. Stir over a gentle heat until the sugar has dissolved and all the ingredients are well combined.
Bring to a gentle boil and cook for about 15 minutes, until it reaches 250°F or soft ball stage. Remove from the heat and add the vanilla.
Cool for 5 minutes then, using an electric mixer, beat until the fudge is creamy and thick and has lost its gloss. This will take about 10 minutes.
Pour the fudge over the biscuit base and smooth out with a spatula. Set aside to cool and refrigerate to set.
Cut slice into squares and store in an airtight container in the refrigerator.