In a medium saucepan, combine all the syrup ingredients and bring to a boil.
Reduce heat to low and simmer until mixture is reduced by one third, about 25 minutes.
Strain the mixture and refrigerate until cooled. Check the syrup's consistency. It should be like honey. If too thin, return it to pan and reduce for a few more minutes. If too thick, add a little water. Set aside.
Slice off the tops and bottoms of the oranges. Then remove all the peel and pith around the oranges.
Slice along the sides of each segment and pull out the segments.
Repeat with lemons.
Spoon the syrup onto a plate and arrange the orange and lemon segments over it. Sprinkle mint leaves on top.