Preheat the oven to 180°C and grease and line an 18 x 28cm baking tin with non-stick baking paper.
Melt the chocolate with the coconut oil in a bowl set over a saucepan. Whisk in all the dry ingredients off the heat, then finally the eggs. At this stage it might look like everything has gone wrong as the mixture thickens and the oil appears to separate from the eggs — keep whisking for a couple more minutes and it will all come together.
Pour the mixture into the prepared tin and bake for 25-30 minutes depending on your preferred texture — they will firm up a little as they cool, so don't overbake them.
Leave the mixture to cool in the tin for 10 minutes then cut into 12 squares or more and place on a wire rack to cool.