Instructions:
- Line an 8x8 inch baking pan with parchment paper, leaving an overhang on two sides. Lightly grease any exposed edges.
- Make the Pistachio Paste: In a food processor, combine the 80g pistachios and 30g sugar. Blitz until finely ground. Slowly drizzle in the oil and almond extract while processing until a thick, slightly coarse paste forms. Set aside.
- Melt the Base: Combine the white chocolate chips, butter, and sweetened condensed milk in a heavy-bottomed saucepan over low to medium-low heat. Stir constantly until the chocolate and butter are fully melted and the mixture is smooth and homogenous. Do not allow it to boil.
- Cook the Fudge: Increase the heat slightly to medium-low. Continue stirring vigorously for approximately 5–8 minutes until the mixture thickens considerably and pulls away from the bottom and sides of the pan when scraped.
- Flavour the Base: Remove the pan from the heat immediately. Stir in the vanilla extract and salt.
- Divide and Flavour: Pour about two-thirds (2/3) of the hot fudge base mixture into the prepared pan and spread evenly.
- Create the Swirl: Take the remaining one-third (1/3) of the fudge base still in the pot. Stir the reserved pistachio paste into this smaller portion until well combined. If using, add the green food colouring now.
- Marble: Dollop spoonfuls of the pistachio mixture over the base layer. Use a knife or skewer to gently swirl the two colours together once or twice. Avoid over-mixing to maintain distinct marbling.
- Chill & Garnish: Sprinkle the top evenly with the roughly chopped pistachios. Allow to cool slightly at room temperature for about 30 minutes, then refrigerate to set completely (minimum 4 hours).
- Cut and Serve: Once firm, use the parchment handles to lift the fudge block out. Slice into neat squares using a sharp, warm knife for the cleanest results.