Sieve the flour, Colman's mustard powder and baking powder together.
Rub in the diced butter till the mixture resembles fine breadcrumbs.
Whisk the egg together with the cream and milk. Briefly mix this through the flour to form a dough. Don’t over mix.
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 180c for 15-18 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!