Toss together crumbs and melted butter. Reserve 1/4 cup of crumb mixture. Press remaining crumbs into 9x9x2 inch baking pan. Spread with softened ice cream and freeze.
Melt the stick of butter and chocolate over low heat. Cool a few minutes and then slowly stir mixture into egg yolks with powdered sugar and vanilla. Cool thoroughly. Meanwhile, beat egg whites till stiff peaks form. Beat chocolate mixture till smooth, then fold in egg whites.
Spread chocolate mixture over ice cream. Top with reserved crumb mixture and freeze.