Brownie is one of the most famous American desserts. According to various sources, the origin of brownie is the result of an omission.
Preheat oven at 350 F (convection mode ideally).
Melt the chocolate in a bain-marie and add the butter until it melts. Remove from heat and let cool.
Beat the eggs and sugar for 5 minutes.
Gently mix the melted chocolate and butter with the eggs.
Stir in vanilla, flour and pecans and mix to obtain a homogeneous dough.
Line an 8x12 inch rectangular mold with parchment paper.
Pour in the mixture and bake in the oven for about 25 minutes.
Test the baking is done by poking with the tip of a knife in the center of the brownie. It must come out dry.
Unmold when the brownie is completely cooled down, then cut into squares.
Brownie can be enjoyed as is, or accompanied by vanilla ice cream, custard or whipped cream.