Heat oven to 200ºC Beat whits to soft peaks. Gradually add sugar, 1 tablespoon at a time, beating 1 minute after each addition to form a stiff meringue. Fold in nuts. Spread into well-buttered 23 cm pie pan w/ sides extending over the rim. Bake 10 minutes or untill lightly browned. Remove & cool. Fill w/ icecream; cover tightly; freeze.
In saucepan, melt butter; stir in sugar and cook until dissolved. Slowly mix in half & half and cook one minute, stirring constantly. Stir in vanilla & nuts; cool slightly. When ready to serve, pour over the frozen pie.