My gluten free chocolate traybake recipe is lovely and moist - like a cross between a brownie and a chocolate cake! It's dairy free and low FODMAP too.
Preheat oven to 160C Fan. Prepare your baking tin with parchment / baking paper. My tin is about 8 inches x 12 inches, so the popular 9x13 tin would be fine I'm sure.
If you are making your own buttermilk - put 1-2 tbsp of lemon juice in a jug and then fill it up to 85ml with milk (any milk will work - if you can have dairy, whole milk works best but I've made it with almond milk and its perfect too). Put your buttermilk to one side until you need it.
Melt your dark chocolate and butter in a glass bowl over some boiling water on the heat.
Once melted, make your coffee (1 tbsp to 125ml of hot water) and pour it into your melted chocolate/butter. Mix it together.
In a large bowl, add your flour, bicarbonate of soda, xanthan gum, cocoa powder, light brown and caster sugar. (I always sieve my cocoa powder especially to remove any lumps) Mix together.
In another bowl crack 3 large eggs and add your buttermilk. Mix together until combined.
Next pour your chocolate mixture into your dry mix bowl, followed by your egg/buttermilk mixture. Mix together - I did this by hand so as to not overmix. Mix until combined, make sure you mix all the way to the bottom so theres no dry flour chunks etc.
Spoon/pour your mixture into your pre-prepared tin and then place in the oven for about 1 hour.
Once baked remove from the oven and leave to cool in the tin.
Whilst the cake is cooling you can make your icing. Cream/beat your butter briefly so it softens a little more - your butter (or dairy free alternative should be at room temp).
Sieve your icing sugar and cocoa into a separate bowl and then gradually add it to the butter. Mix thoroughly between each addition until it's all been added.
If the icing is a little too solid add a couple of teaspoons of milk and mix again. Do this until the icing is at the right consistency for you. It should be smooth but not runny, it should hold its shape, but not be too stiff. (If you are making this icing dairy free I'd recommend chilling it again before placing it on the cake so it's more firm)
If you haven't already, now the cake is cooled, remove it from the tin and spread your icing all over the cake - as much or as little as you want. Then sprinkle on any decorations you want - I went for chocolate strands.
Cut into squares and enjoy!