Pre-heat the oven to 180°C (th.6).

Prepare the short-crust pastry by blending all the ingredients with a food-processor. Allow the dough to rest in the refrigirator. 

Lay out the short-crust dough in a flan dish. 

Prick the bottom and sides with a fork, cover with a sheet of baking paper and weigh down with ceramic pastry weights (or dry beans). After 20 minutes, remove the weights and baking paper, and bake for a further 5 minutes, then leave to cool. 

For the Gavottes-chocolate mixture:

Melt the praline and dark chocolate in a pan over a bain-marie. 

Crumble the Gavottes in a large bowl.

Pour the melted chocolate over the crumbled Gavottes, mix-well. Spread the mixture over the piecrust base. 

Leave to set for 30 minutes in the refrigirator. 

Only then prepare the chocolate mousse: 

Break up 140 g of chocolate and melt it with the butter in a pan over a bain-marie.

Separate the egg whites from the yolks (clarify).

Pour the melted chocolate (after it has cooled) into a bowl and stir in 2 egg yolks.

Whisk the 3 egg whites and lightly fold them into the chocolate mixture. 

Spread the chocolate mousse over the Gavottes-chocolate layer of the tart. Refrigerate for 2 hours.

Just before serving, decorate with chocolate chips.

Suggestion: try making your mousse with white chocolate instead of dark, and add some almonds to the Gavottes. If you are short-of-time, use some ready-prepared pure-butter short-crust pastry.