Roll out the pastry and cut out 6 circles to line 6 small tart molds.
Slice the bananas in half lengthwise and cut each half into 3. Heat 20g butter in a frypan and brown the bananas for a few minutes. Set aside.
Melt the chocolate with 20g butter in the microwave. Preheat oven to 180 degrees C. Butter the tart molds with remaining butter and line with the pastry. Sprinkle with 3 teaspoons vanilla sugar.
Arrange the bananas in star patterns in each tart and pour over the melted chocolate. Bake 25 minutes. Let cool then turn out.
Meanwhile, prepare the caramelised pecans. In a saucepan, combine 40g sugar, 2 teaspoons vanilla sugar and the water. Bring to a boil and simmer 1 minute. Reduce heat and add pecans. simmer until caramelised, then transfer to a greased plate. When cool, crush coarsely and sprinkle over the tarts.