Pre-heat the oven to 175°C (fan)
Sieve the flour, xanthan gum, baking powder, baking soda into a large mixing bowl
Add in the chocolate chips and 3/4 of the mini eggs to the bowl containing the flour mixture and place to one side
In a heatproof bowl, melt the butter in the microwave using short bursts of heating
Add the sugar to the bowl with the melted butter and mix until combined
Add the egg, oil, salt and vanilla extract to the butter and sugar mix and whisk in until combined
Little by little, fold in the flour mixture into the bowl with the eggs, butter and sugar
Line a baking tray with greaseproof paper and pour in the batter, evening out with a spatula
Bake for approximately 20 minutes
Quickly add the remaining 1/4 of the mini eggs to the top of the part-baked squares and press down gently
Bake for a further 8-12 minutes (28-32 minutes total) until the top is soft but baked
Remove from the oven and leave to completely cool in the brownie tray (~ 30 minutes) before cutting
Cut into 9 equal squares and enjoy!
