Preheat oven to 400°F (200°C) and lightly oil an 8 inch (20 cm) cast iron skillet.
In a large bowl, whisk together the flour, baking powder, and salt.
Cut the cold butter into the flour mixture using your fingers or a pastry cutter, mixing lightly until the mixture looks crumbly and no large pieces of butter remain.
Add the cheese to the bowl and stir to combine.
In another bowl, whisk the eggs and milk until mixed.
Add the milk mixture to the flour mixture and mix with your hands until almost incorporated, but some streaks of flour remain.
Turn the dough out onto a lightly floured surface and gently knead a couple of times, until the dough comes together into a ball.
Shape the dough into an 8 inch (20 cm) round.
Place the disc of dough into the skillet and score into 8 equal wedges with a sharp knife, only cutting about halfway through the dough.
Brush the tops with milk and top with flaky salt if desired.
Bake for 30 minutes, or until golden in colour.
Cool the biscuits for 10 minutes in the skillet before removing and cooling fully on a wire rack. Store any leftovers in a sealed container at room temperature for up to 3 days or freeze up to a month.