Preheat oven to 135º C
Melt 100 grams chocolate with vanilla over very low heat
In the bowl of an electric mixer on slow speed, mix egg whites, almonds and sugar until well blended.
With the machine still running, add the melted chocolate mixture.
Continue beating until thoroughly mixed.
Spoon the batter onto a greased baking sheet, allowing 1 headed tablespoon of batter for each macaroon.
Bake for about 15 to 18 minutes, or just until the macaroons are set. They should be slightly firm but not dry.
Transfer to a rack to cool. Meanwhile prepare the filling.
Melt 50 grams chocolate over very low heat.
Add crème fraiche to melted chocolate for filling.
Stir until well blended.
When the macaroons and the filling have cooled, spread a heaped teaspoon of the filling on half the macraroons.
Cover each with a second macaroon, making a sort of sandwich.
Serve immediately.