Cream butter and sugar together, add in an egg and mix till combined, add in flour and leave it to rest.
Once rested, press it into 25cm tart shell and blind bake in a preheated 240 degree F oven (140 degrees Celsius, or 280 Fahrenheit) for 20 minutes. Then bake for another 20 minutes. Once baked, leave to cool.
Boil cream and once it reaches 80 degrees, remove from heat.
Add in chocolate and sugar, mix well. After mixing, stir in butter, espresso and a pinch of salt.
Pour filling into the cooled crust and let it set.
Garnish with cocoa powder before serving.
