Preheat the oven to 170°C / 150°C fan.
Grease and line a small square baking tin - approx 7 x 7" to 8 x 8".
Sieve flour and cocoa powder into a large bowl.
Add xanthan gum, baking powder, salt, cornstarch and sugar. Whisk together thoroughly.
Add the beaten eggs, butter, oil, orange extract and almond milk. Mix well.
Stir in the chopped chocolate orange.
Pour mixture into lined tin and bake for 25-30 minutes. Less time will result in a squishier middle whilst cooking for longer will produce a firmer brownie.
Leave to cool in the tin for 5 minutes, then transfer to a cooling rack.
Wait until fully cooled (ideally 1-2 hours) before cutting. They will be very soft when fresh out the oven and begin to hold their shape better as they cool.
Cut into 12 and push a mini chocolate orange segment into the top of each brownie (optional).