Sift the flour and salt into a large mixing bowl. Place the cubed 10 grams of butter into the flour and rub in with fingertips until mixture resembles fine breadcrumbs.
Add water and use a cutting motion with a knife to form a dough. Turn dough onto a lightly floured surface and knead gently until smooth. Cover with plastic wrap and rest in refrigerator for 30 minutes.
Remove dough from fridge and discard plastic wrap, with a lightly floured rolling pin roll dough out to a 10 x 30cm rectangle. Set aside.
Place the 70 grams of butter between 2 pieces of plastic wrap, gently begin to tap with rolling pin until you achieve a 8 x 9cm rectangle.
Lay dough on a lightly floured surface with the 10cm edge closet to you. Remove plastic wrap from butter rectangle and place butter in the centre of the dough. Now fold the end closet to you over the butter, then repeat with other side. (The butter should now be enclosed in the dough.
Turn dough 90 degrees clockwise and gently press edges together. Gently flatten out butter by tapping with a floured rolling pin. Roll dough out to a 10 x 30cm rectangle and repeat folding process as above. Cover dough with plastic wrap and refrigerate for 30 minutes to allow butter to firm again.
Remove from fridge and repeat rolling and folding process 2 more times. Cover with plastic wrap again and place in refrigerator for a further 30 minutes to rest. Remove from fridge and repeat rolling and folding process 2 more times. Cover with plastic wrap and place in fridge for another 30 minutes. (In total the dough should have been folded and rolled 6 times).
Preheat oven to 200C. Grease then line a baking sheet.
Remove dough from fridge and roll out to a 10 x 30cm rectangle (or to a 1/2cm thickness).
Cut 2.5cm strips, then twist and lay on baking sheet. Sprinkle with cayenne pepper, if using, next sprinkle with parmesan cheese and then finally top with cheddar cheese.
Bake for 10 minutes or until golden brown and cheese has melted.