Frozen Maple Walnut Mousse Pie

This frozen pie layers a light, airy maple mousse over a chocolate crumb crust, topped with whipped cream, chopped walnuts, and chocolate shavings. The mousse starts with a cooked custard base of egg yolks and real maple syrup, thickened in a double boiler, then lightened with stiff egg whites and whipped topping.

Cooking the yolk-maple mixture in a double boiler is what gives the mousse its body. Direct heat would scramble the eggs, but the gentle steam thickens them into a smooth, golden custard that holds its structure even after freezing.

Folding is where this comes together or falls apart. Combine the cooled custard with the whipped egg whites and whipped topping using slow, sweeping motions from the bottom up. Stirring deflates everything, and a flat mousse is just frozen pudding.

Four hours minimum in the freezer. The mousse needs to set completely solid for clean slices.

Chef Tips

• Cool the custard to room temperature before folding in the whites. Warm custard melts the whipped topping and deflates the whites.
• Beat egg whites to stiff, glossy peaks. Soft peaks won’t hold up during folding and the mousse will be thin.
• Let the pie sit at room temperature for 5 to 10 minutes before slicing. A brief thaw makes cutting easier and improves the texture.

Variations

• Use a graham cracker crust instead of chocolate for a more classic maple-walnut flavor.
• Swap walnuts for pecans for a butter pecan twist.
• Drizzle extra maple syrup over each slice when serving for an intensified maple hit.