Nibblous | cheese, onion and olive scones

Ingredients

• 1½ oz (40 g) Parmesan, grated
• 1½ oz (40 g) strong Cheddar, grated
• 1 medium onion, diced
• 6 black olives, pitted and chopped
• 1 tablespoon olive oil
• 6 oz (175 g) self-raising flour
• ½ level teaspoon salt
• ½ level teaspoon mustard powder
• ½ level teaspoon cayenne pepper
• 1 oz (25 g) butter
• 1 large egg
• approximately 2-3 tablespoons milk
• freshly milled black pepper