Prepare the Base: Place the digestive biscuits in a food processor and blitz until they form fine crumbs. Alternatively, put them in a sealed plastic bag and crush them with a rolling pin. Transfer the crumbs to a medium bowl, add the demerara sugar (if using), and pour in the melted butter. Mix with a fork until the crumbs are evenly coated and resemble wet sand.

Form the Base: Press the buttery crumb mixture firmly and evenly into the bottom of a 20x20cm square dish or a 2-litre trifle bowl. Use the back of a spoon or the bottom of a glass to compact it well. Place the dish in the refrigerator to firm up while you prepare the filling.

Beat the Cream Cheese: In a large mixing bowl, add the room temperature cream cheese. It’s crucial that it’s soft to avoid lumps. Beat it with an electric mixer on a medium speed for 2-3 minutes until it's completely smooth and creamy.

Add Flavourings: Scrape down the sides of the bowl. Add the sifted icing sugar, vanilla bean paste, and lemon juice to the cream cheese. Beat again on a low speed until just combined, then increase the speed to medium and beat for another minute until everything is well incorporated and silky. I find that sifting the icing sugar is a small step that makes a huge difference in the final texture.

Whip the Double Cream: In a separate, clean bowl, pour in the cold double cream. Using the electric mixer (with clean beaters), whip the cream on a medium-high speed until it forms stiff peaks. This should take about 3-4 minutes. Be careful not to over-whip it. For more on this technique, Serious Eats has a great guide on achieving perfect whipped cream.

Combine the Filling: Gently fold about one-third of the whipped cream into the cream cheese mixture using a spatula to lighten it. Then, add the remaining whipped cream and fold carefully until there are no more white streaks. The goal is to keep the mixture as airy as possible.

Assemble the Pudding: Retrieve your dish from the fridge. Spoon the cheesecake filling over the chilled biscuit base and spread it into an even layer using an offset spatula or the back of a spoon.

Top and Chill: Gently spread the thawed Cool Whip or whipped topping over the cheesecake layer. Cover the dish with cling film (be careful not to let it touch the topping) and refrigerate for at least 4 hours, or preferably overnight. This chilling time is essential for the flavours to meld and the filling to set properly.

Serve: Just before serving, you can garnish your Cheesecake Pudding Cool Whip with fresh raspberries, blueberries, grated chocolate, or even some leftover biscuit crumbs.