Cheesy Bites

INGREDIENTS
plain flour (175g)
generous pinch of cayenne pepper
generous pinch of mustard powder
1/2 tsp of salt
cold cubed butter (125g)
chunk of blue cheese, such as stilton (50g)
chunk of cheddar cheese (75g)
walnuts, shelled (75g)
1 egg
2 tbsp of poppy seeds