Mix together the butter, granulated sugar and cocoa powder. Then add the egg and flour. Knead without overworking until the dough is homogenous. Place in the fridge at 5°C (41°F). Roll out the dough to a thickness of 3 mm then cut out four 16 cm circles. Leave to rest in a cold place for 1 hr, then cook in a fan oven at 180°C (356°F) for about 14 min.
Heat the milk and cream and infuse the Genmaicha tea for 3 to 4 min then strain. Make a custard with the milk, cream, granulated sugar, and egg yolks. Add the gelatine mix. Pour into 14 cm ‘flexipan’ insert moulds. Place in the freezer.
Make a custard with the milk, granulated sugar and egg yolks. Pour onto the chocolate, mix, and blend in the butter.
Heat the milk and infuse the Genmaicha tea for 3 to 4 min and strain. Make a custard cooked at 85°C (185°F) with the Genmaicha tea infusion, egg yolks, and granulated sugar. Pour the custard onto the dark chocolate, mix in the gelatine mix. Chill at 30°C (86°F) and work in the whipped cream.
Melt together at 40°C (104°F).
Arrange the mousse in a half dome in a plastic mould. Add the frozen crème brulée filling then cover with the marquise up to the top of the mould. Place in the freezer. Take out of the mould, assemble on the chocolate short pastry bases, and spray with the dark chocolate using a spray gun. Decorate with a chocolate shaving and a bit of Genmaicha tea.