Mix the flour and cheese together in a bowl, add butter to the cheese and flour mix and rub with fingertips until combined

Stir in the egg yolk and mix to form a dough, wrap the dough in clingfilm and leave to chill in fridge for about 30 minute

Preheat oven to 200°F gas mark 6 lightly grease several baking trays

On a floured surface roll out the dough thinly stamp out 6cm rounds re rolling the trimmings to make about 35 rounds

Place the rounds on baking trays and sprinkle the sesame seeds over the top of them

Bake in preheated oven for 10 minute until light golden in colour, place on wire rack and leave to cool