Preheat oven to 350º Fahrenheit or 175º Celsius.
Prep a baking tray or cake tin with baking spray or greaseproof paper.
In a saucepan, melt the butter, dark chocolate and marmalade.
In a mixing bowl or stand mixer, whisk the eggs, light brown sugar and caster sugar together until light and fluffy.
Add the plain flour and cocoa powder to the eggs, and mix together until combined.
Add the melted butter, chocolate and marmalade to the dry ingredients and mix together until well combined.
Pour the mixture into the prepared tin and zest an orange over the top of the mixture. Place the mini chocolate orange segments on top of the brownie mixture.
Bake the chocolate orange brownies for 30-35 minutes. When you take them out of the oven they will seem under cooked, but they will firm up as they cool down. Allow to cool and then cut into portions.