Preheat oven to 160 degrees celsius (fan-forced). Grease and line a large 32cm x 28cm rectangular slice tin with baking paper.
Place the butter into the Thermomix bowl and melt for 2 mins, Speed 2, 100 degrees (or until melted). Add the chocolate ripple biscuits into the Thermomix bowl and crush for 6 seconds, Speed 10. Firmly press the biscuit mixture into the prepared tin and set aside.
Place the white chocolate into a clean and dry Thermomix bowl. Melt for 3 minutes, 60 degrees, Speed 1 (or until melted). Allow to cool slightly.
Add the cream cheese, sour cream, caster sugar, eggs, and vanilla extract. Mix for 15 seconds, Speed 5. Scrape down the sides of the bowl and repeat for a further 15 seconds (or until smooth).
Fold the raspberries gently through with a spatula.
Pour the mixture into the prepared tin and spread out evenly with a spoon.
Optional - if using raspberry coulis, dot about 6-8 tablespoons of coulis randomly over the top the the slice. Then, use a knife to gently swirl the mixture a few times. Don't overmix the coulis or it will lose the pretty swirl effect.
Place into the oven for 40-50 minutes or until firm in the centre. Note: if you notice the slice is over-browning and still isn't cooked through, place a sheet of foil loosely over the top and continue cooking. Once completely cooled, place in the fridge for at least 4 hours (preferably overnight) before cutting into slices.
Decorate with extra raspberries, berry coulis and melted white chocolate drizzled over the top (optional).