1. To make the rough puff pastry, put the flour, salt and butter into a bowl and rub in the butter using your fingertips, until the pieces are roughly half the size. Add the water and mix to a dough. On a floured surface, roll the dough out to a neat rectangle, about 50 x 20cm. Fold the top third down, then the bottom third up over the top. Wrap in cling film and rest in the fridge for 30 minutes. Give the dough a quarter-turn, then roll out and fold as before, twice more. Now dust your work surface with icing sugar and roll out the pastry to the thickness of a £1 coin. Dust the pastry heavily with icing sugar and roll up, like a big sausage. Wrap in cling film and chill in the freezer.
2. Preheat your oven to 200°C/Fan 180°C/Gas Mark 6. Line a baking sheet with a non-stick baking mat or silicone paper. Unwrap the pastry roll and cut into six slices, the thickness of a £1 coin. Lay these on the baking sheet. (Freeze the rest of the pastry roll for another day.) Bake the pastry discs for eight to 10 minutes until crisp and golden. Carefully transfer to a wire rack to cool. Keep in an airtight container until ready to serve.
3. To make the custard, pour the cream and elderflower cordial into a pan and bring to the boil over a medium heat. Meanwhile, whisk the eggs and sugar together in a large bowl. Pour on the hot cream mix, whisking as you do so, then add the lemon juice. Pour into a thermomix set at 90°C and cook on full speed for five minutes. Or cook, stirring over a low heat, until the custard reaches 90°C. Immediately pour into six serving dishes. Let cool slightly and then place in the fridge to set; this will take two hours.
4. For the strawberry champagne sorbet, put all the ingredients into a pan and bring to a simmer over a medium heat. Cook for 15 minutes. Take off the heat and blitz the mixture with a hand blender, then pass through a sieve into a jug and leave to cool. Once cooled, churn in an ice-cream machine until firm, then transfer the sorbet to a suitable container and freeze until ready to serve.
5. To make the syrup, put the strawberries, elderflower cordial and glucose into a pan, bring to a simmer and cook for 10 minutes. Remove from the heat and leave to cool, then pass the syrup through a sieve into a jug. Set aside for serving.
6. Put the fresh strawberries into a bowl, add some of the syrup and toss carefully to dress. Remove the elderflower custards from the fridge and arrange the strawberries equally on top of them. Spoon a neat scoop of strawberry sorbet on top of each pile of strawberries and finish with a puff pastry disc. Serve immediately.