Place cookie sheet on middle oven rack in oven to preheat; heat oven to 375°F. In 1-quart saucepan, melt chocolate chips and 2 tablespoons of the butter over low heat, stirring constantly, until smooth. In medium bowl, mix remaining 6 tablespoons butter and 2/3 cup sugar with wire whisk until light and fluffy. Stir in almonds, 1 egg, the egg yolk and melted chocolate until well blended. Spread mixture evenly over bottom of crust-lined pan.