1. For the biscuits, preheat the oven to 180C/350F/gas mark 4. Rub the butter into the flour until the mixture looks like fine breadcrumbs. Stir in the Parmesan, salt, pepper and cayenne, then work together into a ball. Turn out on to a lightly floured work surface and knead briefly until smooth.
2. Flatten the ball of dough slightly and then roll out thinly between two sheets of cling film this will make rolling out this short mixture very much easier.
3. Lift off the top piece of cling film and cut out 7.5cm/3in rounds using a plain pastry cutter. Carefully transfer to a lightly buttered baking sheet. Re-roll the trimming and cut out more biscuits you should make about 10-12 biscuits in total.
4. Bake the biscuits for 12-15 minutes until golden and leave to cool on the baking sheet. Meanwhile whip the cream with the lemon juice and some seasoning until it just forms peaks. Stir in the chopped chives.
5. To serve, spoon a little of the cream on to each biscuit. Cover with pieces of softly folded smoked salmon and serve garnished with whole chives together with plenty of the watercress.