First up let's make the sponge; preheat the oven to 180°C/160°C/Gas Mark 4. Grab a 10x8” baking tray and grease and line, now we’re ready to bake!
First thing; mix your coffee with 100ml boiling water in a small bowl and set aside to cool. Pop all your dry ingredients into a large bowl and mix. Make a well in the centre and add the oil, Vanilla Extract, eggs, buttermilk and coffee mixture and whisk together until thoroughly mixed, your mixture will be quite runny.
Pour the mixture into your prepared baking tray and pop in the oven to bake for 25-30 minutes. To make sure your sponge is baked pop a skewer into the centre of the sponge and it should come out clean. Leave to cool in the tin for 15 minutes, then remove, and pop onto a wire rack to cool completely.
Pop your Buttercream into a large bowl and add your salted caramel sauce. Mix together to combine and loosen the buttercream. Cover until your sponge is cool.
Once your sponge is cool, cut a circle the same diameter as the top of your jar (cut enough circles for the number of cake jars you are making). Crumble up the remaining sponge to large crumbs; you can do this either with your hands or a fork. Set aside in a bowl.
Take your jars and pop a few spoonfuls of sponge in the base of each to create an even sponge base layer. Drizzle some caramel sauce on top of the sponge and then pipe or spoon a layer of buttercream on top. Repeat again adding another layer of crumbled sponge, caramel and buttercream. Finish with a circle of sponge on top (that you previously cut out). – if you are using taller jars you might need to add another layer of crumbled sponge and buttercream before popping on the sponge circle.
Pop the remaining buttercream into a piping bag fitted with an open star nozzle and pipe a buttercream swirl on top of each jar – if you do not have a piping bag you can add a spoonful of buttercream on top and smooth out using a palette knife or back of a spoon. Drizzle over any remaining caramel sauce and finish with Chocolatey Caramel Crunch Sprinkles!