Peel banana and mash into puree, set aside; Remove pistachio shell, place in oven preheated to 100℃ (upper/lower element) for 10 minutes; once ready, crush into small pieces and set aside. Place gelatin in ice water until softened. Place milk in double boiler to heat, add gelatin and stir until completely incorporated. Allow the milk to cool in room temperature, then separate into 2 150g portions; add banana puree in one portion and pistachios in the other. Add 3g of lemon juice, 3g of rum nd 150g of cream in banana milk, blend evenly until it turns into mousse texture. Add 3g of lemon juice, 2g of rum and 150g of cream in pistachio milk, blend evenly until it turns into mousse texture. Squeeze half of banana mousse into mold, fill remaining mold with pistachio mousse. Refrigerate mousse for 2 hours; once removed, use hair dryer or hot towel to unmold; decorate mousse with pistachios before serving.