Preheat the oven to 180C/350F/Gas 4.
Rub the butter into the flour, by hand or in a food processor, until the mixture looks like fine breadcrumbs.
Stir in the parmesan, seasoning and cayenne pepper.
Work the mixture together into a ball and then knead briefly on a work surface lightly dusted with flour until smooth.
Cut the dough in half, flatten each piece slightly, then roll out thinly between 2 large sheets of cling film.
Lift off the top piece of cling film and cut into 5cm/2in biscuits.
Carefully lift them onto a lightly buttered baking sheet, then knead together and re-roll the trimmings to make more biscuits. You should make about 30 biscuits in total.
Bake the biscuits for 8-10 minutes until crisp and golden. Leave to cool on the baking sheets. Store in an airtight tin.