Sieve the flour, Colman's mustard powder and baking powder together.
Rub in the diced butter till the mixture resembles fine bread crumbs.
Add the grated cheddar & chives to the flour mix, then gradually add the milk until you have a soft but not wet dough, all the milk may not be required.
On a floured surface roll out to 2.5cm thickness. Cut out scones with a 50mm ring. Re roll left over pieces. Remember to handle and rework your dough as little as possible. This gives the best rise and texture.
Bake in oven at 220c for 12-14 minutes. For the last 5 minutes brush with and egg wash (1 egg yolk beaten with a pinch of Colman's mustard powder)
Leave to cool on wire rack for 10 minutes. Enjoy as part of a delicious afternoon tea!