Banana Chocolate Bavarois

Cover a medium size round pan with a plastic foil, cover evenly the sides of the pan taking cake that the foil comes out of the pan. Combine the crushed cookies with the melted butter. Pour in the prepared pan and cover the entire bottom with the back of a glass. Pour in the refrigerator.
Pour the banana and the lemon juice into the blender and blend to reduce it in pure. Pour the gelatin leafs with 2 tbsp water in a small bowl. Pour the water with the sugar into a deep and heavy saucepan and bring to boil on a high heat, cook until the sugar melts. Add drained gelatin leafs and stir until the gelatin melts too. Stir in the banana pure. Stir in the whipped whipping cream. Pour this mixture over the crust and keep in refrigerator about 1 hour.
Prepare the chocolate bavarois: Pour the gelatin leafs in a small bowl with water. After 2 minutes dry it and combine with 20 ml of warm water. Stir until dissolves. Stir in the whipped whipping cream and add the melted chocolate. Pour this chocolate mixture over the banana mixture into the pan. Refrigerate overnight.
Before serving, remove the Bavarois from the pan by taking it with the plastic foil that comes out the pan. Very carefuly remove the foil and transfer the bavarois onto a serving plate. Slace the half banana and sprinkle with the juice of half lemon to prevent of browning. Cover the top of the bavarois with melted chocolate, the banana slices and a handful of chopped walnuts. Slice and serve!