soft ganache (two weights of cream and one weight of chocolate), medium ganache (equal weights of cream and chocolate), and firm ganache (one weight of cream and two weights of chocolate).
Soft ganache can be chilled and whipped like whipped cream to create fabulous chocolate mousses (see the simple chocolate mousse recipe below) - elegant, luscious desserts. Soft ganache mousses can be used as cake fillings or as parts of impressive creations. You can make "chocolate whipped cream" mousses with bittersweet, semisweet or white chocolate ganache.
MEDIUM AND FIRM
Both medium and firm ganaches can be used as icings for cakes. In my favorite ganache icing, satin-smooth, shiny ganache glaze (recipe below), I use a ratio of cream to chocolate that is halfway between medium and firm ganache.
Firm ganache can become truffles or a torte with the addition of eggs. Sherry Yard has a wonderful recipe for baked whisky tortes using a firm ganache in "The Secrets of Baking: Simple Techniques for Sophisticated Desserts" (Houghton Mifflin).
Other ingredients, such as corn syrup, also go into ganache creations. Any time that you want a soft shine - for example, in a ganache icing - think corn syrup. As my friend Harold McGee puts it, "Corn syrup is a liquid that attracts water and fills in spaces between fine sugar particles to produce a glass-smooth surface." The corn syrup in the satin-smooth, shiny ganache gives a deep shine to the dark surface.
I used to think that ganache icings had to be nothing but cream and chocolate, but then I read Miss Yard's work. (She is the executive pastry chef at Spago.) In her ganache glaze, she adds apricot jelly, which sweetens, adds subtle flavors and adds a little pectin to slightly firm the glaze. What a great idea!
The classic method of preparing ganache is to place the chopped chocolate in a heatproof bowl, bring the heavy cream to a boil, pour the hot cream over the chocolate, and stir rapidly together until it is smooth. I know that this method has been passed down for generations, but it can have problems.
If the cream and chocolate are not successfully combined, the ganache can separate with an oily, shiny glaze on top, or it can contain little hard, undissolved chocolate specks. These are two separate problems. The oil on top occurs when the emulsion (a blending of two liquids that ordinarily do not go together, such as fat and water) breaks and the liquids start to separate. The undissolved chocolate specks are what chefs call "seizing." It is this seizing that I think can be a problem when pouring the hot cream over the chocolate.
Young pastry chefs are taught to approach ganache worrying about the emulsion, but it is the seizing that I am always concerned about. If even for a split second there is too little water-type liquid and too many cocoa particles in the mixture, it can result in little hard chocolate specks.
In seizing, beautiful, satiny, flowing melted chocolate can suddenly become a rock-hard, grainy mass. Chocolate is composed of fine, dry particles (cocoa and sugar) in rich fat (cocoa butter). With melted chocolate, a few drops of water, or even steam, can cause these dry particles to glue together.
An example of this is your sugar bowl. When you dip the spoon that you used to stir your coffee back into the sugar bowl several times, you have dry particles and a small amount of moisture and you get clumps of dried sugar particles stuck together. But if you pour a cup of boiling water into the sugar bowl, you'll get no clumps. There is plenty of water to dissolve all of the sugar.
There is plenty of water-type liquid in the cream to prevent the cocoa particles from gluing together (seizing) but, if the liquid is added to the chocolate, there can be a split second when there are many dry cocoa particles and too little liquid so that tiny stuck-together particles can form. I feel that it is much safer to add the chocolate to the cream, as I do in both recipes below.
As long as the chocolate is finely chopped, the temperature is hot enough to melt the chocolate, and the ganache is stirred, I have not seen problems with the ganache breaking, but I have seen problems with chocolate specks even with experts.
In a tiny kitchen in Erice, Italy, I watched as a French restaurant owner-chef poured the boiling cream over chopped chocolate while a famous French pastry chef stirred vigorously. The pastry chef got a product that he was unhappy with two out of five times. He pointed out the tiniest chocolate specks in the otherwise smooth mixture.
There were only the three of us there; the two chefs spoke little or no English, and I spoke no French. So, I could not ask my questions or suggest something to try. After all, this was one of the most famous pastry chefs in France, so I remained respectfully silent.
A reasonably fail-safe procedure for adding the hot cream to the chocolate is in a food processor. With the processor running, pour the boiling cream down the feed tube onto the finely chopped chocolate. Chocolate expert Alice Medrich does caution that this should take no longer than 15 seconds. You need to get the liquid in fast.
In the ganache recipes below (an easy chocolate mousse and a magnificent perfectly smooth icing that looks as if it came from an expensive bakery), I add the chocolate to the cream - not the cream to the chocolate.
Simple chocolate mousse
This is essentially chocolate heavy cream that is chilled well and whipped. It is important to finely chop the chocolate. I cut the chocolate into pieces and process it in the food processor with the steel blade until very finely chopped.
Makes about 4 servings.
2 cups heavy cream
2 tablespoons sugar
8 ounces, very finely chopped semisweet chocolate
In a large saucepan, heat the cream to a boil, stir in the sugar, allow to stand 1 to 2 minutes off the heat, and then dump in the finely chopped chocolate. Shake to settle the chocolate in the cream.
Allow to stand 1 to 2 minutes for the chocolate to melt, then gently stir together. When this is thoroughly combined, allow to cool, cover and refrigerate overnight.
Simply whip the cold, thin ganache to soft peaks as if it were heavy cream. Do not overwhip; it will become firmer as it stands in the refrigerator. Pour into parfait glasses, chill and serve. If desired, garnish with whipped cream or chocolate shavings.
Satin-smooth, shiny ganache glaze
With this icing, a rank beginner can make a magnificent cake with a perfect satin-smooth icing that looks as if it came from an expensive bakery.
Spreading icing is an art that takes practice. So, I was thrilled when I learned what I call a double-icing technique in Alice Medrich's book, "Cocolat: Extraordinary Chocolate Desserts" (Morrow). This ganache and this technique allow anyone to make a perfectly smooth icing.
Corn syrup is the secret to a handsome surface gloss, and chopping the chocolate very finely is the secret to easy blending.
This icing can be used on layer cakes, tortes, muffins and many desserts.
Makes about 3 cups of icing (enough to ice a 9-inch, double layered cake).
16 ounces semisweet chocolate (I love Guittard, but it may be difficult to find in your area.)
1/3 cup red currant or apple jelly
1 1/2 cups (12 ounces) heavy cream
1/3 cup sugar
2 tablespoons light corn syrup
Place the chocolate in the food processor with the steel blade. Process chocolate to chop very finely.
In a large saucepan over medium heat, heat the jelly just to melt. Stir in the cream, sugar and corn syrup, and bring carefully to a boil. Remove from the heat and allow to cool for 1 minute.
All at once, dump in the chocolate, spreading it across the top of the hot cream mixture. Jar the pan to settle the chocolate. Allow to stand about 1 minute; then, starting in the middle, slowly stir to blend the cream and chocolate together. Stir until well blended, but be careful not to incorporate air bubbles.
Put the cake to be frosted on a cake cardboard exactly the size of the cake. Strain half of the icing into a measuring cup with a spout and set aside. Allow the other half to cool.
When it is about body temperature (ideally, about 90 degrees), ice the cake with it, using an offset spatula as needed to smooth the sides. Refrigerate for 30 minutes to set the icing.
The strained half needs to be warm and thin enough to pour easily. Heat briefly. Do not use a spatula at all this time. Pour the warm ganache on the cake and tilt to spread.
• Food scientist Shirley O. Corriher is author of "CookWise: The Hows and Whys of Successful Cooking" (William Morrow).