Make the chocolate mousse. Put a medium mixing bowl in the refrigerator to chill. Bring about 1 inch of water to a simmer in a saucepan; put the chocolate and butter in a medium heat-proof bowl and set it over the pan, making sure that it doesn't touch the water. Stir with a wooden spoon until the chocolate is melted and the mixture is smooth. Remove the bowl from the heat and let the mixture cool slightly. Then whisk the egg yolks into the chocolate one at a time, beating until smooth after each addition. Set aside. In a separate bowl, whisk the egg whites until foamy. Add the cream of tartar and beat until soft peaks form. Gradually beat in the 1/4 cup sugar and continue beating until stiff peaks form. In the chilled mixing bowl, beat the heavy cream until it begins to thicken up. Add the remaining 2 tablespoons sugar and the vanilla, and continue beating until the cream holds soft peaks.

Now combine the three mixtures: Stir a spoonful of the egg whites into the chocolate mixture to lighten it; then fold in the rest. Fold in the whipped cream, taking care not to overwork the mousse. Chill in the refrigerator for 1 to 2 hours.

Prepare the raisins. Reduce the oven temperature to 200 degrees F. Spread the grapes out on a roasting tray and bake them in the oven for 2 hours. Remove and set aside to cool.

Toast the brioche. Preheat the oven to 350 degrees F. Thinly slice the brioche roll, place the slices on a sheet tray, and drizzle them with olive oil. Bake in the oven until golden brown, 7 to 8 minutes. Set aside and allow to cool.

Candy the orange slices. In a medium saucepan, combine the sugar and 1 1/2 cups of water and bring to a boil over high heat. Add the orange slices and return to a boil. Then reduce the heat to medium and simmer, turning the oranges occasionally, until the liquid has reduced to a thin syrup and the oranges have turned translucent, about 25 minutes. When done, the orange slices will be tender and the sauce will be thick like a glaze. Transfer the oranges to a tray lined with waxed paper and allow to cool.

To assemble the rocky road, smear chocolate mousse on the center of each plate. Top with raisins, popcorn, cashews, and brioche toast. Garnish with mint buds and orange slices, and season with fleur de sel and olive oil.