Lightly butter 6 (4-ounce) souffle dishes and dust with 1 tablespoon of the sugar, knocking out any excess. Make collars from aluminum foil strips or pieces of parchment paper and wrap around the dishes so that the upper edges are 1-inch above the tops. Secure with string and set aside.

In a medium heatproof bowl, beat the egg yolks with 1/4 cup of the remaining sugar and 1/2 teaspoon of the orange zest. Whisk in the Grand Marnier and place the bowl over a pot of barely simmering water and cook, whisking constantly, until the mixture is thick and light in color like whipped cream, 4 to 5 minutes. Remove from the heat.

In a large bowl, beat the egg whites with the salt until foamy. Beating, gradually add the remaining 1/4 cup sugar until glossy peaks are formed. Set aside.

In a third bowl, beat the cream until it forms soft peaks.

Gently fold the whipped cream into the egg yolk mixture, and then fold in the meringue. Spoon the mixture into the prepared souffle dishes, leveling off the tops. Freeze until the souffles are set, at least 4 hours or overnight.

To serve, remove the foil collars from the dishes and place each on a dessert plate. Garnish each portion with orange zest strips and serve cold.