These angels get their iridescent glow from sparkling sugar, sold at some gourmet grocers and at cake decorating and kitchen shops. You can order 8 ounces for $6 or 3.3 ounces for $4 from La Cuisine - The Cook's Resource in Alexandria, Virginia, at 1-800-521-1176.
Beat butter at medium speed with an electric mixer until creamy. Gradually add 2/3 cup sugar, beating well. Add egg yolk and vanilla; beat 1 minute or until yellow disappears.
Combine flour and salt; gradually add to butter mixture, beating at low speed just until dry ingredients are moistened. Beat at medium speed 2 minutes. Divide dough into 3 portions; shape each into a ball, and wrap in plastic wrap. Chill 1 hour.
Line 3 baking sheets with parchment paper. Sprinkle parchment with flour, and unwrap each dough portion on a lightly floured surface. Roll each into a 9- x 6-inch rectangle (about 1/4 inch thick). Cut dough using a angel-shaped cookie cutter. Reserve trimmings. Freeze angels on baking sheets 15 minutes; slide angels at least 3 inches apart.
Whisk together egg and whipping cream. Brush angel cookies lightly with mixture, and sprinkle with sparkling sugar.
Bake at 350° for 20 minutes or until golden brown; cool on pan 10 minutes. Transfer cookies with parchment paper to a wire rack to cool.
Press together reserved dough trimmings; roll out on a lightly floured parchment paper-lined baking sheet to 1/4-inch thickness; cut with a 1-inch star-shaped cutter. Remove and discard trimmings. Brush stars lightly with egg mixture, and sprinkle with sparkling sugar, reserving remaining sugar.
Bake at 350° for 12 minutes or until stars are golden brown. Remove with parchment paper to a wire rack to cool.
Brush upper one-third of back of each angel lightly with corn syrup, and sprinkle with reserved sparkling sugar, if desired. Let dry.
Microwave candy coating in a 4-cup glass measuring cup at HIGH 1 1/2 minutes or until melted, stirring twice. Pour into a small heavy-duty zip-top plastic bag; seal. Snip a tiny hole in 1 corner of bag, and drizzle a small amount onto backs of 6 stars (reserve extra stars for other uses). Attach 1 star to center of each angel.
Drizzle in desired design over wings. Make small dots with coating along upper edge of halos. Let stand until hard. Store in an airtight container up to 1 week, or freeze up to 6 months.