Directions: Place cheese, mustard, cayenne pepper and flour in a bowl and mix to combine. Rub butter in, using your fingertips until mixture resembles coarse breadcrumbs.
Mix in egg yolk and enough water to form a soft dough with a metal spatula or round-ended knife.
Turn dough onto a lightly floured surface bd knead gently until smooth.
Wrap in plastic food wrap and refrigerate for 30 minutes. Roll out and used as desired.