Sift the flour and salt into a large bowl.

Coarsely grate the butter into the flour (dip the block of butter into the flour every few seconds to stop it sticking to the grater). Stir in so the pieces are separate and coated in flour.

Stir in the Cheddar and Parmesan cheeses.

Sprinkle over 4 tbsp of the iced water then use a round bladed knife to start bringing the mixture together. Add enough water, a little at a time, until you can use your hands to form it into a dough.

Pat the dough into a thick oblong block, cut in 2, then wrap each piece in foil. Chill in the fridge for at least 30 minutes. Dough can also be frozen.

Preheat the oven to 200°C /180° fan/Gas 6 /400° F.

Lightly grease some baking trays or line them with baking parchment.

Lightly flour your worksurface.

Take one piece of dough from the fridge, unwrap and lightly sprinkle with flour.

Roll into a rough rectangle approximately 5 mm thick (this makes cheese straws that are crisp, flaky and a little tender inside; roll to 2.5 mm for crispness all the way through).

Cut the dough into a neat rectangle, reserving any scraps of dough.

Brush with beaten egg then finely grate extra Parmesan all over it.

Cut the dough into straws 0.5 - 1 cm wide and 10 - 15 cm long, as preferred.

Transfer to the prepared baking trays, leaving just a little space between them. Cheese straws can be frozen at this point.

Bake in the oven until risen, golden and cooked all the way through (approx. 15 minutes - a little longer if baking from frozen).

Tip: if you'll be storing and reheating later, be sure not to overbake.

Carefully transfer to a wire rack where they'll crisp up a little more.

Meanwhile, repeat the process with the remaining half of the dough plus any leftover scraps.

These cheese straws must be eaten warm to be enjoyed at their best: if necessary, reheat in an air fryer preheated at 200° C then cooked for 1½ - 2½ minutes, or in a regular oven at 180°C /160° fan/Gas 4 /350° F for 3 - 6 minutes.

To store, make sure the cheese straws are completely cold before transferring to an airtight container where they should keep for up to a week or frozen for a month.