A Baker's (now owned by kraft foods) employee named Sam German developed a chocolate recipe that was sweeter than semi-sweet chocolate, as well as containing a blend of chocolate liquor, sugar, cocoa butter, flavorings, and lecithin. Baker's honored Sam by naming the chocolate that he created Baker's German's Chocolate.
In 1957 the recipe was published in a Dallas newspaper, although nobody is sure exactly when the recipe was originally created. Generally Foods - who had bought the brand - noticed that alot of people liked the recipe and started a PR campaign for German's Chocolate using the recipe. They started sending it to newspapers all over - and people liked it. At some point the "'s" got dropped from the name, introducing all of the confusion we have about the origin of the cake today.
References:
http://en.wikipedia.org/wiki/German_chocolate_cake
http://en.wikipedia.org/wiki/Walter_Baker_%26_Company
http://www.joyofbaking.com/GermanChocolate.html
What you are asking for is physically impossible.
There is a reason why the color system when working with physical dyes (as opposed to colored light) is called additive. You cannot take out a color which is already there. When we are talking about a cake, cocoa powder or pure chocolate can be considered a pigment, and Guiness a pre-dyed liquid.
The first of three methods would be to add your cocoa and guiness as they are, but try to mix them with other stuff so You can use them to make new, darker colors by mixing in other pigments, or lighter colors by diluting them. You can certainly mix white cake batter with food coloring of other colors (yellow) and the right amount of chocolate to achieve a caramel color, but this will be very far from the proportion which gives you a chocolate cake which tastes of chocolate and has the right texture.
The second method would be to try to discolor the cocoa and guiness. But the problem is that you cannot change the color of a pigment without changing it chemically. Assuming that somebody can come up with a process which can bleach cocoa or chocolate, it will certainly change the taste a lot, if it is food safe at all. Probably not doable in a home kitchen either.
The third thing would be to replace the chocolate entirely. But there is no substitute which tastes like chocolate. I have never heard of the "chocolate extract" which Catija refers to, but even in cases where a flavor is dominated by a single note which is easily reproduced chemically (vanilla, banana, etc.), the stuff which makes up that single note does not taste like the real deal. And if something had exactly the same composition as cocoa, it would not only taste like cocoa, it would be cocoa, with its normal color. And that part concerns the flavor only. Even cocoa powder changes the texture of a cake, while real chocolate changes it much, much more. If you could make chocolate-perfumed cake, it would still not have the mouthfeel of chocolate cake.
Beside all the reasons why you cannot get chocolate flavor paired with a strange color, there is something else: Human perception is not limited to one sense. People rely a lot on vision when eating, and the experience of eating a strange-colored chocolate cake will not be the same "taste" experience as eating correctly colored chocolate cake. There are some fun studies with gummy bears and red/white wines which got lots of press about that, and some marketing gimmicks like the recent Mystery Mueller Milch in Germany, but this is not the place to elaborate. If you want your guests to enjoy a chocolate cake, you have to make a real chocolate cake, with the correct flavor, texture and color.
For completeness, you have the following options instead of making an amber chocolate cake (some already suggested in comments):
- make a non-chocolate cake and use food coloring to make it amber
- make a standard-color chocolate cake and decorate it with amber icing (again, use food coloring)
- make a standard-color chocolate cake with any color icing, or without icing, and have some color contrast at the wedding :)
Best Answer
I have seen this happening more than once. While I don't know the whole theory behind it, each time it happened, there was something just below the hole, let's call it "the lump".
What I think happens is that the lump is too heavy. When the batter below it tries to rise, it doesn't have the strength to push up the lump. This could be combined with differences in heat transfer throughout the batter vs. on the batter-lump transition in preventing rising (I am certain they exist, but I don't know whether they have an effect at all). The result is a hole where the batter didn't rise, surrounded by nicely risen batter.
As to where the lump comes from: you say "chocolate and pear cake". If you have pear pieces in the batter, right under the surface, they can do this. I have certainly seen it happen when the recipe includes fruit pieces in the batter. If there are no pear pieces, my second guess is badly dissolved flour. The directions for this type of cake normally include folding the whites very gently, and generally erring on the side of too little whisking. This could contribute to uneven batter texture, resulting in lumps.
In the second case, the cake may have some less-than-pleasant pieces, but will still be mostly good. If it is fruit, the holes are purely a cosmetic problem. So not much harm done either way, unless you are shooting for a prize at a baking competition.