In a small saucepan set over medium-high heat, bring the maple syrup to a boil, and cook until it registers 240 degrees on a candy thermometer, about 15 minutes. Remove from heat.
While your maple syrup is heating, in the bowl of an electric mixer fitted with the whisk attachment, beat the eggs on high speed until light and fluffy, about 5 minutes.
With the mixer running, slowly pour syrup down the side of the bowl in a slow, steady stream, until completely incorporated, about 1 minute. Continue beating for an additional 4 to 5 minutes. Add butter, one piece at a time, until thoroughly incorporated. Then add heavy cream slowly and whip until it is well combined and fluffy.