This tart is best served still warm from the oven.
- Heat the oven to 200C.
- Using an electric beater, cream the butter until fluffy, then add the sugar. Beat until the mixture is fluffy again. Beat in the egg whites and essence until smooth. Mix in the walnuts, then pour the batter into the cooked shell. Spread the mixture evenly.
- Bake for 20 minutes or until the mixture is bubbling and golden brown. Remove the tart from the oven and allow it to cool. Serve with whipped cream.