Wash 1 orange, grate dry and cut into thin slices. Dab slices dry and turn them in 100 g sugar. Place on a baking tray lined with baking paper. After about 2 hours, dab dry again and turn in the sugar.
Let orange slices dry overnight. The next day, turn again in sugar.
Chopping chocolate. Cut butter into pieces. Melt the chocolate and butter in a wide saucepan over low heat while stirring. Peel the rest of the orange and cut into slices.
Beat the eggs, brown sugar and salt in a bowl with the whisk of the hand mixer for 3-4 minutes until creamy. Remove the chocolate and butter mixture from the heat and immediately pour into the egg mixture and stir in.
Mix flour, cocoa and baking powder. Quickly fold into the chocolate-egg mixture.
Pour the dough into a greased springform pan (26 cm Ø), spread orange slices on top. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 25 minutes.
Remove and let it cool down on a cake rack.
Soak gelatine in cold water. Dissolve espresso powder in coffee liqueur, mix with mascarpone and 50 g sugar. Whip the cream with the whisks of the hand mixer until stiff. Dissolve the gelatine.
Stir in 5 tablespoons of the mascarpone mass, stir into the remaining mascarpone. Carefully fold in the cream. Spread the cream on the brownie base. Chill for approx. 2 hours.
Carefully remove the cake from the springform pan and place it on a cake plate. Spread the caramel on the cake. Cut the sugared orange slices into quarters and decorate the cake with them.