1. Heat oven to 350 degrees F. Line 24 muffin cups with baking liners. Coat liners with cooking spray. Melt chocolate and butter in heavy saucepan over low heat, stirring, until smooth. Remove from heat. Let cool.
2. In a large bowl, with electric mixer on high, beat egg yolks and 1/4 cup sugar until very thick and pale, about 3 minutes. Fold in melted chocolate and vanilla. Using clean, dry beaters, beat egg whites and remaining 1/4 cup sugar in bowl until stiff peaks form, about 2 minutes. Fold egg-white mixture into chocolate mixture until well combined. Pour into baking liners.
3. Bake 25 minutes, or until toothpick inserted in center of a cupcake comes out clean. Tint whipped cream pale pink; frost cooled cupcakes. Use chocolate morsels for eyes, and pipe a smile onto each cupcake face with tubed icing.