The original ambrosia recipe is simply a layering of orange slices, sugar, and toasted unsweetened coconut. Over the years, folks began to add pineapple, maraschino cherries, and whipped cream to create more of a fruit salad, but the name stuck.
Bring sugar and 1/2 cup water to a boil; stir until sugar dissolves. Boil 5 minutes. Remove from heat; steep 1/2 cup mint 20 minutes. Strain syrup; discard solids. Cool syrup completely.
Toss together citrus sections and 1/4 cup syrup. Cover and chill 8 hours, stirring occasionally. (Reserve remaining syrup for another use.) Chop remaining 1/4 cup mint; toss with fruit. Serve with Chantilly Cream.
Fresh Mint Syrup: Steep fresh mint in hot sugar syrup to make a delightful simple syrup up to a week before Christmas. Section the citrus, and toss it with syrup the day before.