How to Make It
Line a rimmed baking sheet with parchment paper. In a small saucepan, dissolve the sugar in the water and simmer over moderate heat until a rich brown caramel forms, about 6 minutes. Add the hazelnuts and pistachios and stir to coat. Using a fork or slotted spoon, working quickly, transfer a few nuts at a time to the parchment paper and separate them. Let cool completely, about 25 minutes.
In a small saucepan, boil the water with the sugar until reduced by one-fourth, about 12 minutes. Stir in the cornstarch slurry and simmer until the sauce thickens, about 30 seconds. Remove from the heat and stir in the ras el hanout. Let cool to room temperature.
Preheat the oven to 350°. Arrange the bananas on 2 large rimmed baking sheets. Using a skewer or paring knife, poke the bananas all over, about 1 inch deep and 1 inch apart. Stud the bananas with the coffee beans, candied orange peel, vanilla beans and cinnamon sticks. Roast the bananas for about 20 minutes, until very tender.
Cut 6 of the bananas in half crosswise. Spoon the spiced syrup onto plates. Arrange a whole and halved banana on each plate. Garnish with the candied nuts and serve.
Ras el hanout, a Moroccan spice mixture containing up to 50 spices (including ginger and anise), is available from Middle Eastern markets and kalustyans.com.