Heat the oven to 350 °F.

1. Line a sheet pan with a silicone baking mat or parchment.
2. Microwave the corn syrup for 30 seconds in a medium bowl. Stir-in the puffed rice to coat then spread on the sheet pan. Sprinkle with the granulated sugar.
3. Bake the puffed rice for 10 minutes until gently browned.
4. Melt the dark chocolate in the microwave.
5. Allow the rice to cool completely then break into small pieces on the mat. Drizzle with the melted chocolate and refrigerate until cooled completely.

With the oven still at 350 °F, the cake can be baked while the rice is baking and cooling.

1. Line the bottom of a 8" - 9" springform pan with parchment. Mist the pan with cooking spray and coat with flour.
2. Whisk together all dry ingredients in a large bowl.
3. In a measuring cup, beat the egg then mix-in the oil and buttermilk.
4. Pour the egg-oil-buttermilk mixture into the dry ingredients and fold until moistened.
5. Add half of the hot coffee to the bowl and gently mix to loosen the batter. Add the remaining hot coffee and mix until the batter is smooth.
6. Transfer the batter to the prepared springform pan then bake for 20 to 30 minutes until a toothpick when inserted comes out clean.
7. Allow the cake to cool for 15 minutes before opening the springform and removing it. Lift the parchment onto a rack to cool.

Finally, the peanut butter mousse can be made while the other components are cooling.

1. Pour the cold water over the gelatin in a small ramekin. Whisk well until dissolved then set aside.
2. Heat the milk in a small sauce pan until it begins to bubble at the edges — do not boil. Remove from heat when ready.
3. In a medium bowl, whisk the egg yolks and grantulated sugar until dissolved. Continue whisking while slowly drizzling the warm milk into the egg and sugar mixture. Once all milk has been added, continue whisking until uniform then transfer the mixture back into the sauce pan.
4. Put the sauce pan over medium-low heat and heat the mixture until it thickens enough to coat the back of a spoon. Remove from heat.
5. Add the peanut butter and gelatine mixture to the warm custard and mix until uniform. Allow the custard mixture to cool completely.
6. Once cooled, add the heavy cream to a separate mixing bowl (large enough for the custard and the cream) and whip the cream until medium-soft peaks form.
7. In batches, fold the cooled custard into the whipped cream. Keep folding until the mixture is just combined.

For service:

1. Cut rounds from the cake to fit in the base of the ramekins. You may need to slice the top off the cake to get a uniform height to the cake layer. Cool the ramekins in the refrigerator until the mousse is ready.
2. Divide the mousse between the ramekins, then cool again (for at least 30 minutes this time).
3. Optional: top the mousse with chocolate ganache.
4. Garnish with the puffed rice then cool in the refrigerator before serving.