Preheat the oven to 180°C conventional (160°C fan-forced). Spray the bottom of a square cake tin with olive oil spray, then line with baking paper so it comes up the sides a little.
Throw all the ingredients except the Easter eggs into a large mixing bowl. Combine. Beat with an electric mixer for about 3–4 minutes until well mixed. Pour into the cake tin.
125 g butter, 1 cup brown sugar, 0.5 cup caster sugar, 3 eggs, 2 cups plain flour, 0.333 cup cocoa powder, 1 tsp bicarbonate of soda, 0.25 tsp sea salt, 0.667 cup sour cream, 0.5 cup water
Bake for 40–45 minutes. Remove and let cool.
While the cake is cooking, make the icing. Combine all the ingredients in a saucepan and gently warm over low heat until combined. Place in the fridge for 10 minutes so it thickens up slightly. Spread over the cake.
100 g dark chocolate, 60 g butter, 0.5 cup icing sugar, 0.25 cup sour cream
Decorate with any Easter eggs or candies you like!
Easter eggs