To make the compote, remove the stems from the cherries, and pit each one using a cherry pitter or use a sharp knife to slice each cherry in half and prise out the stone. Add to a small saucepan with the sugar, water and cinnamon.
Cook on low heat for 4 to 5 minutes, stirring often until the cherries have softened and broken down and the liquid is bubbling. Let the compote cool completely at room temperature (about 30 mins) and the liquid will thicken to a saucy consistency.
To make the mousse, melt the chocolate in a microwave-safe bowl in two 10 second increments on high, stirring in between each. Do not overheat the chocolate and when it's almost fully melted, stir gently to smoothen out any lumps.
Using a hand mixer and mixing bowl, beat the cream on high speed for 3 to 4 minutes until it thickens to stiff peaks with very slightly rounded tops.
Add a spoon of the whipped cream to the melted chocolate and stir gently to help loosen it. Fold in the rest of the cream gradually, working gently but quickly till you have a smooth and fluffy mousse. Refrigerate for 10 to 15 minutes before assembly. The mousse will thicken further the longer it's chilled.
To assemble, get out two medium sized jars or glasses and add 3 to 4 tablespoons of the cake crumbs at the base of each. Top with 2 tablespoons of compote and then about 3 generous tablespoons of the mousse. Repeat until all of it is used up. Top with fresh cherries and dig in!
Store in the refrigerator, loosely covered for 3 to 4 days but the layers will be most defined when freshly assembled. The mousse and cake will take on a delicious fudgy texture after a day so let the jars sit at room temperature for 10 to 15 minutes before you eat. Enjoy!