In a water bath, melt the dark chocolate with the butter. Remove from heat and let cool.
In a bowl, mix the eggs with the sugar, maple sugar, salt and vanilla.
Add the melted chocolate mixture to the bowl and stir. Add the flour and stir again, until a smooth preparation is obtained.
Line a 33 cm x 23 cm (13 in x 9 in.) mold with parchment paper and pour the pulp into it. Equalize the surface.
Bake for 30 to 35 minutes. Remove from the oven and let cool on a rack. Place 1 hour in the refrigerator, then cut into 20 to 25 pieces.
In a second bowl, whisk the cream using the electric mixer until soft peaks are obtained. Add the icing sugar and orange peel, then whisk until firm peaks are obtained. Reserve in the cool.
In a third bowl, whisk the mascarpone with the sugar and cocoa. Stir in a third of the whipped cream, gently folding the preparation with a spatula.
In a large glass dish with a capacity of about 3 liters (12 cups), place half of the brownie pieces. Couvrir half of the mascarpone cream, then half of the remaining whipped cream. Cover with the rest of the brownie pieces, then the rest of the mascarpone cream and the rest of the whipped cream. Refrigerate for 4 to 6 hours.
When serving, decorate the trifle with chocolate chips and orange peels.