Break up biscuits into smaller pieces. Set the bowl aside.

Toss cocoa powder and sugar in a saucepan, stirring until mixed. Then, pour in water. Add butter, put it on medium heat, and wait 5 minutes until it boils. Keep stirring the whole time. Add some rum extract. Let it cool for 5 minutes.

Pour the chocolate syrup (Step 2) over the biscuit pieces (Step 1). Mix up with a spoon.

Place a cake ring onto your serving plate. Line it with acetate sheets. Dump the biscuit and syrup mix into the cake ring and firmly press it onto the bottom.

Refrigerate it (covered) during the next steps.

Dissolve gelatin powder in a bowl of cold water. Let it sit and puff up for about 5 minutes.

Grab another bowl. Mix the mascarpone cheese, instant coffee, and powdered sugar until smooth. Throw in a splash of vanilla extract.

Gently heat the gelatin until it melts completely. Pour this into the mascarpone mix and stir.

Whip cooled cream into the mousse until you see soft peaks forming.

Pour the mousse over your biscuit cake. Refrigerate it (covered) for 4 hours to a whole day.

Toss cream and chocolate in a heat-safe bowl. Fill a pan with steaming water, place the bowl over it, and melt on low heat.

Pour the creamy chocolate ganache all over your cake evenly. Refrigerate for 30 minutes.

Optional: Top it off with chocolate rocks or coffee whipped cream. Enjoy!