Preheat the oven to 180°C/fan 160°C/gas mark 4. Using your hands, roll out the pastry into a 3cm-diameter cylinder shape. Cut it into 12 discs, about ¾cm wide.
Sift some of the 150g icing sugar out on to a clean work surface. Then place a pastry disc on the sugar and, pressing down, roll swiftly in one direction. Turn it over, sift over more icing sugar and roll the pastry in the opposite direction. The aim is to get these discs as thin as possible. Use strong strokes with the rolling pin to achieve this. Repeat this until you have a 1mm thin oval strip about 15cm long. Then repeat with the remaining pastry discs and icing sugar until you have 12 evenly sized sugared pastry strips.
Place the pastry strips on silicone mats and put in the preheated oven for around 12 minutes, or until they become golden brown. Remove from the oven and cool on a rack for 5 minutes.
To make the coulis, heat 2 tablespoons of water and the sugar in a small saucepan until the sugar has dissolved. Add the raspberries and cornflour and continue to cook, on a medium heat, until the raspberries break down and the mixture thickens. This should take 5–8 minutes.
Remove the pan from the heat and stir in the framboise, then leave to cool before blitzing the mixture in the food processor. Pass the coulis through a sieve for an even smoother finish.
When the pastry strips have cooled, assemble the finished dish. Place one of the pastry strips on a plate and decorate it with piped whipped cream and raspberry halves. Repeat, placing a second pastry strip on top to form a second layer and decorating it as before. Top with a third pastry strip. Repeat for 3 more plates, using all 12 pastry strips. Either spoon over the cold coulis or serve it on the side.