Preheat the air fryer to 200°C (400°F).
Place the dry ingredients into a large mixing bowl and give them a mix.
175 g Self Raising Flour, ¼ teaspoon Salt, ⅛ teaspoon Cayenne Pepper, ¼ teaspoon Mustard Powder, ½ teaspoon Baking Powder
Add the chilled cubed butter to the mixing bowl and rub it in with your hands until you get fine breadcrumbs form.
55 g Unsalted Butter
Stir in the grated cheese (reserving a few heaped tablespoons for the tops).
120 g Extra Mature Cheddar Cheese
Heat the milk in the microwave for 20 seconds, squeeze in a little lemon juice (about ¼ teaspoon) and leave it to stand for 2-3 minutes. Pour the soured milk into the mixing bowl and use a metal dinner knife to stir it in.
85 ml Whole Milk, ¼ teaspoon Lemon Juice
Once the scone dough has started to come together, use your hands to bring it together into a ball.
Lightly flour your work surface then knead the scone dough for a few seconds to cover it in flour. Shape the dough into a disc about 3 cm thick with your hands then stamp out 5 scones with a 5cm cookie cutter. You'll need to keep reforming the dough into a disc with your hands until you have used it all up.
2 tablespoon Plain Flour
Using a pastry brush, glaze the tops of the scones with milk then sprinkle over the reserved grated cheese.
2 tablespoon Milk, 120 g Extra Mature Cheddar Cheese
Place the scones in your air fryer basket and air fry for 8 minutes until risen and golden brown.