Preheat oven (electric cooker: 180 °C/circulating air: 160 °C/gas: see manufacturer). Coarsely chop the walnuts, up to 12 pieces. Peel bananas and crush them in a bowl with a fork. Beat the sugar, 1 packet of vanilla sugar and margarine until creamy with the whisks of the mixer.
Stir into the bananas, add the soy drink. Fold flour and baking powder into the banana mixture. Mix all ingredients to a smooth dough.
Spread the dough evenly over 12 tins and bake in a hot oven for 18-20 minutes. Take the tartlets out of the oven and let them cool down.
Defrost frozen raspberries. Puree up to 12 pieces and pass through a fine sieve. Whip the whipping cream and 1 packet of vanilla sugar with the whisks of the mixer. Stir the raspberry puree into the cream.
Pour into the freezer bag, cut off a small corner. Decorate the tartlets with the cream, place 1 raspberry on each.