Spread 7 cups flour in each of three 13x9-in. pans and 4 cups flour in a 9-in. square pan. Carefully wash the egg in a mild bleach solution (1 teaspoon chlorine bleach to 1 qt. warm water); dry. Press washed egg halfway into the flour to form an impression. Repeat 35 times, 2-in. apart; set aside.
In a small bowl, sprinkle the gelatin over cold water; set aside. In a large saucepan, combine the sugar, 1/2 cup corn syrup and hot water. Bring to a boil over medium heat, stirring constantly, until a candy thermometer reads 238° (soft-ball stage). Remove from the heat; stir in remaining corn syrup.
Pour into a large bowl. Add reserved gelatin, 1 tablespoon at a time, beating on high speed until candy is thick and has cooled to lukewarm, about 10 minutes. Beat in vanilla.
Spoon lukewarm gelatin mixture into egg depressions; dust with flour. Let stand for 3-4 hours or until set.
Brush excess flour off marshmallow eggs. Dip each egg in chocolate candy coating. Place flat side down on waxed paper. Let stand until set. Drizzle each coloured candy coating over eggs.
Test Kitchen Tips
Silicone egg moulds are available and can be used instead of the flour.