Chopping chocolate. Cut butter into pieces. Melt the chocolate and butter in a pot at low heat. Mix flour, cocoa and baking powder. Beat the eggs, brown sugar and 1 pinch of salt in a bowl with the whisk of the hand mixer for about 5 minutes until creamy.
Remove the chocolate-butter mixture from the stove and immediately pour into the egg mixture and stir in. Quickly fold the flour mixture into the chocolate-egg mixture.
Put the dough into a greased, square springform pan (24 x 24 cm). Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 25 minutes. Take out, immediately sprinkle with 60 ml espresso and let it cool down on a cake rack.
For the espresso syrup, caramelise 100 g sugar in a pan. Deglaze with 60 ml espresso and 100 ml water. Leave to simmer until the caramel has dissolved, allow to cool.
Remove the bottom from the mould. Peel and slice the bananas. Sprinkle with lemon juice. Spread the bananas on the brownie. Beat the egg white until stiff, add 1 pinch of salt and 200 g sugar.
Add meringue to the bananas and spread. Chill for about 1 hour. Meringue mass with a crème-brûlée distiller. Carefully cut into pieces with a moistened knife. Add the espresso-caramel sauce.