Sponge

1. Preheat the oven to 160°C fan and line a 20cm x 30cm baking tin with greaseproof baking paper.
2. Add the coffee granules and boiling water to a small bowl and mix until the granules have dissolved. Set aside.
3. Sieve the flour, cocoa powder and bicarbonate of soda into a large mixing bowl and combine.
4. Make a well in the centre and add the rest of the ingredients.
5. Mix until smooth. If using a stand mixer, mix on a slow speed.
6. Add the mixture to the baking tin and bake in the oven for approximately 20 mins.
7. Leave to cool in the tin for 10 mins, then transfer to a wire rack.
8. Once fully cool, wrap the sponge in cling film and pop it in the fridge for at least 30 mins. This will make the sponge easier to cut later.

Chocolate Ganache

1. Chop up the chocolate into small pieces and add it to a microwave safe bowl.
2. Pour the cream over the top and heat for 30 – 40 seconds in the microwave on a high heat setting. You want the cream to be hot but not boiling.
3. Remove and stir until smooth. If there are still some lumps of chocolate, pop the mixture into the microwave for 20 seconds and stir.
4. Cool the ganache in the fridge until it starts to thicken and is cold to the touch. Stir occasionally. You can quicken the process by placing the ganache in the freezer but check on it frequently, you don’t want it too thick.
5. Whip the ganache using a stand mixer or electric whisk. You want the ganache to end up with the consistency of whipped cream.
6. Add the whipped ganache to a piping bag, either fitted with a large round nozzle or by cutting a hole in the end.

Cake Jar Assembly

1. Cut the chilled sponge into 6 rounds the same width as the jars you are using. Then cut the rounds in half so you end up with 12 mini round sponges.
2. Crumble the remaining sponge.
3. Begin layering your cake jars by adding one round sponge to the bottom of a sterilised jar. You can cut the sponge into quarters to make it easier to add to the jars.
4. Next add 15g of the crumbled biscuits and level the crumbs with a spoon.
5. Pipe a layer of ganache on top of the biscuit crumbs and smooth out with a spoon.
6. Add 10g of mini marshmallows on top of the ganache.
7. Spoon in some cake crumbs to make a layer.
8. Pipe another layer of ganache.
9. Add one more round sponge.
10. Finally top with more ganache and some extra marshmallows.
11. Place a lid on top and repeat for your other jars.