Preheat oven to 350°F (180°C).

Place margarine, potato starch, walnuts and/or almonds in a bowl and crumble between your fingers to create crumbly, sand-like consistency.

Add oil by tablespoonful, and mix between your fingers some more. Small clumps of crumbs should form.

Lay out evenly on a lined baking sheet. You can add the slivered pecans or almonds at this point if you are using.

Bake for 18 minutes, or until edges just begin to brown.

Remove from oven and fluff with a fork to create crumbs. Let cool completely.

Start beating the whites in a large mixing bowl fitted with a beater attachment.

Add the sugar in a slow stream.

Add remaining ingredients in the order they appear, and beat for a full 10 minutes.

Place half the batter into a 9 x 13-inch container, and sprinkle with a little less than half the crumb mixture.

Add remaining batter, and top with remaining crumbs.

Freeze, and scoop into cups before serving. (It’s so soft that it scoops easily, even when frozen.)

You may want to create small parfait glasses, putting in mousse, then crumbs, then mousse, and topping with crumbs. Let individual parfaits stand at room temperature for 15–20 minutes before serving.