Preheat oven to 350°F/177°C. Grease and line a 9-inch square pan. Set aside.
In a bowl, cream butter, add eggs one at a time. Add in the orange liqueur, juice, zest and extract.
Combine brownie mix, stir until smooth. Pour brownie batter into prepared pan.
Bake for 20-25 minutes or until brownie is set.
Serve with candied orange slices.