Preheat the oven to 200°C/400°F/Mark 6. Sprinkle the pastry board and the pastry with flour. Roll the pastry into a round 25cm (10in) across. You will now have a flat disc of pastry. Place it on a baking-sheet and prick here and there with a fork. Put it in the refrigerator for 10 minutes then bake in the oven for 15 minutes. Allow to cool.
Meanwhile cut each half walnut into four pieces. Put the lumps of sugar in the saucepan with 4tablespoons of cold water. Place over a medium heat and allow to caramelise to a light chestnut brown. Now tip in the walnuts and coat them with the caramel, stirring them about with the spatula so that they are well coated.
Away from the heat add the honey and cream, mixing them in well with the spatula until the mixture has cooled to lukewarm.
Spread the mixture in an even layer on the cooked pastry. Allow to rest for 20 minutes before serving.