Preheat the oven to 175°C / 350°F. Place the pre-baked sweet shortcrust pastry shell in a cake ring on a baking sheet, or prepare one large ramekin.

Create a bain-marie by bringing a small amount of water to a gentle simmer in the saucepan. Set a heatproof bowl over the pan without letting its base touch the water.

Melt the 190 g dark chocolate with the 80 g salted butter in the heatproof bowl. Stir until the mixture is smooth and fully combined.

Remove the chocolate mixture from the bain-marie. Whisk in the 80 g egg yolks until glossy and homogeneous.

Place the 120 g egg whites in a clean mixing bowl. Whip them with the electric mixer until soft peaks form.

Gradually add the 50 g brown sugar while whipping the egg whites. Continue whipping until stiff, glossy peaks form.

Fold one-third of the whipped egg whites into the chocolate mixture to loosen it. Gently fold in the remaining whipped whites without deflating the mousse.

Add a pinch of fleur de sel to the mousse. Fold gently just until the salt is evenly distributed.

Add the 250 g toasted pecans, 250 g almonds, 150 g caramel, and a pinch of fleur de sel to the food processor. Blend until a thick, smooth praline paste forms.

Spread the pecan almond praline over the base of the pastry shell or in the ramekin. Smooth the surface with a rubber spatula.

Pour the chocolate mousse over the praline layer. Level the top gently with the rubber spatula.

Bake at 175°C / 350°F for 8 to 12 minutes, until the edges are set while the centre remains soft. Remove the tart or ramekin from the oven.

Let the baked mousse cool before serving. Slice the tart or spoon the mousse from the ramekin and enjoy.