Using a stand mixer fitted with the whip attachment, whip the heavy cream, creme fraiche, Grand Marnier, and orange blossom water until the mixture holds soft peaks. Set aside.
In a small saucepan over medium heat, combine the honey, corn syrup, and sugar. Cook without stirring until the mixture reaches 248°F on a candy thermometer.
Meanwhile, when the sugar reaches 238°F, in the bowl of a stand mixer, fitted with the whip attachment, whip the egg whites until they hold medium peaks. When the honey syrup reaches 248°F, reduce the speed of the mixer to low and drizzle the hot syrup into the whites. Increase the mixer speed to high and whip until the mixture is cool, about 5 minutes.
Fold 1/3 of the cream into the egg whites. Fold the remaining whipped cream into the whites.
Spoon the mixture into the prepared pan, over the sorbet. Tap the pan gently on the counter to make sure the mousse is even. Use an offset spatula to smooth the top flat. Freeze for at least 6 hours.