The maple frosting for the maple sugar cake is boiled icing. The boiling is done by the maple syrup with one-quarter cup of sugar mixed in. The cook is supposed to "boil it until the mixture spins a thread or registers 220 degrees on a candy thermometer." Huh?
Well, as usual, if you really want to know what's going on, consult the expert. The Joy of Cooking will tell you what boiled icing is, and what all this mixture spins a thread stuff is. The first thing the book tells us is, "Never ruin a good cake with a doubtful icing." Now exactly what constitutes a doubtful icing is not explained, but, it's good advice nonetheless.
Boiled icing, Rombauer and Backer tell us, is "Based on the principle known as Italian Meringue,--the cooking of egg whites by beating into them gradually a hot but not boiling syrup." Okay? Clear enough there. Now we get to this "spin a thread" business. "Cook the syrup to 238 to 240 degrees." Now I guess there was a time when every kitchen had a candy thermometer. My mother had one, although she probably only made candy three times in her entire life. It lived in its box in the drawer to the left of the stove, the one that held odd implements like the meat mallet. The box was decorated with gaily colored candies, and I dreamed of being able to make those candies. Alas, it was not to be.
By the time both she and my sister had died the drawer that held the odd implements in my childhood had graduated to holding the good stainless steel knives, forks and spoons, and the candy thermometer was lost in the mists of time. So, while I was doing all this boiling, I lhad no idea what the temperature of the syrup might be. I also feel that we as a family possess enough cooking equipment, so I was not inclined to rush out to the fancy cooking store on Wisconsin Avenue and shell out for a candy thermometer. The Northeast section does contain candy recipes, so I may get one yet, but not today, Roo dear.
Back to The Joy of Cooking. The sugar syrup "will have gone through a coarse thread stage and when dropped from the edge of a spoon will pull out into thickish threads." Well, I didn't exactly notice the thickish threads. However, I continued bravely boiling, since one of the lessons I have learned from this cooking odyssey is don't stop in the middle. It just takes longer than you think.
"When the thick thread developes a hair-like appendage and curls back upon itself, remove the syrup from the heat." A little thread of sugar dries and curls up off the spoon. Eureka!
What you get after beating the maple and sugar syrup into the egg whites (I doubled the recipe because it seemed skimpy,) is a shiny white icing reminiscient of melted marshmallows. It tastes mildly of maple syrup and hardens a little bit. Follow Mrs. Joy's directions about keeping all the utensils "scrupulously clean," because egg whites can be a pain in the ass and not whip if there is any grease around.
3/4 of a cup maple syrup
1/4 cup sugar
1 egg white
1. Place the syrup and sugar in a small pan and heat until the mixture spins a thread (see above) or registers 220 degrees on a candy thermometer.
2 Immediately pour the syrup slowly into the stiffly beating eff white, continuing to beat until the mixture is cold. (This takes a while, ten minutes maybe.) Makes about two cups.