Preheat the oven to 220°C.
Line two 45cm x 30cm trays and a 25cm springform tin with greaseproof paper and brush with melted butter.
Cream butter and sugar for the joconde paste, beat in egg whites, fold in flour and food colouring.
Pipe swirls of paste onto baking trays and freeze until firm.
Whisk egg whites and granulated sugar until stiff peaks form for the meringue.
Beat almonds, icing sugar, and eggs until fluffy, then mix in flour and cocoa powder.
Fold the meringue and clarified butter into the batter.
Spread batter over the frozen decorations on the trays.
Bake for 5-7 minutes until lightly browned.
Peel off the paper and cut sponge strips and circles to line the tin.
Dissolve gelatine in sieved orange juice over simmering water.
Melt chocolate and stir in orange zest, egg yolks, gelatine, and whipped cream.
Fold in whisked egg whites, pour mousse into the tin, and chill for two hours.
Thicken orange juice and arrowroot in a pan to create the gelée.
Top the cake with cooled gelée, whipped cream, orange curls, and cocoa powder.