You may not know this, but Mexico City is one of the highest altitude national capitals. Denver is called the "Mile High City" because of its altitude (we learned in elementary school that there are 5280 feet in a mile). Mexico City's altitude of 7350 feet makes it the almost-one-and-a-half-mile high city. So here's a little bit of physical science information that you might or might not know: the higher the altitude, the lower the air pressure. Big deal, you may be saying. But if you're trying to cook and even moreso if you're trying to bake, it is a very big deal. Lower air pressure makes water boil at a lower temperature, thus making it more difficult to cook things in or over boiling water--it takes longer because the water is not as hot as one would expect at a lower altitude. Why is this an issue in baking? Well, when water or any other liquid boils, it evaporates. Thus, in baking a cake, for instance, liquid begins evaporating sooner and this can cause the cake to be dry. What's more, lower air pressure also affects the leavening process, where certain ingredients produce gases that make the cake rise. What happens here is that gas is produced faster (which is really what water boiling is as well--water changing from a liquid to a gaseous state), the cake rises faster, but because this is happening at a lower temperature that it would at or near sea level, the rest of the chemical reactions are out of synch. The structure of the cake is created by the starches in the flour, the sugar, and the fats. If the cake rises too fast, the center falls because it isn't as done as it should be. So, there are various adjustments that one can make to a cake recipe to change the chemistry to try to account for the lower boiling, faster rising, etc. (a little more flour, a little less sugar, a higher temperature, a longer cooking time, etc.). Okay, end of first physical science lesson.
Remember above when I said Mexico City's altitude is 7350 feet? Well, to the local population, it's 2240 meters. That's right--they use the dreaded metric system, not only for distance but also for weights and dry volume (grams) and liquid volume (liters). Sure, we know about how much two liters is (a two-liter bottle of Coke/soda/pop--duh!), but how do teaspoons and measuring cups compare? For most of the cake ingredients, if you have measuring cups and spoons for the English system of measurement and your recipe is written in the English system, everything works fine. But if the fat you are using is butter, the usual way it is measured is by the stick (which is 1/4 pound, 1/2 cup, or 8 tablespoons). The wrapper of a stick of butter is conveniently marked into tablespoons with additional markings indicating 1/4 cup and 1/3 cup. But if the butter is sold in a country that uses the metric system (which, by the way, is almost every country in the world except for the US), turns out a box of butter is not one pound and the four sticks of butter in the box are not 1/4 pound each. With nothing to compare it to in the grocery store, the box looked about the right size. However, when I opened it at home, the sticks looked like they were flattened--about the right dimensions in length and width but not in height.
All of this is to say, it's Doug's birthday and he was returning from the US, so I was going to surprise him by baking one of our favorite cakes. First I had to try to buy an appropriate pan for it because, as I may have mentioned previously, there is NOTHING to bake in, in this otherwise very fully-furnished apartment. Last weekend I found a pan that's not exactly right but I thought it would work. First I made sure I could get all of the ingredients for the cake. Then I got my sister to fill in some details in the recipe (via Facebook, of course).
Saturday afternoon I started to bake the cake. First step, as my mother taught me, is turn the oven on. Uh-oh--the oven temperature is measured in degrees Centigrade and my recipe calls for 400 degrees Fahrenheit. Yes, we learned the conversion from Fahrenheit to Centigrade in school, but it's one of those things that I don't really remember. I could figure it out, but I don't remember it. Luckily, though, we now have the internets, so I quickly found a conversion calculator. If I remember correctly, it was 224 degrees C.--something like that. So I turned the oven on to that temperature.
For this particular cake, making the batter involves melting the butter with water and powdered cocoa. After this mixture boils, it's added to the sugar and flour and then the rest of the ingredients are stirred in. So I usually start the butter melting with the water and cocoa, then measure the sugar and flour, etc. I opened the butter box and dumped out the--oops--flattened sticks of butter. Shit! Read on the stick of butter (mantequilla) that it's 90 grams. Great--how much of a quarter pound is that? Internets to the rescue once again. Of course I needed to round somewhat and eyeball where to cut the sticks of butter, but I had enough for both the cake and the icing.
So, how'd the cake turn out? Well, let me tell you that although I knew that high altitude baking is tricky, I learned all of the specifics that are in the first part of this post WHILE THE CAKE WAS IN THE OVEN. When I noticed that it looked funny (like, the outside edge was tall and the middle 90 percent of the cake was much shorter). Needless to say, it's not the right consistency, but it tastes better than several others I made experimentally when I was 13 or 14 (once I got baking powder and baking soda mixed up and used the wrong one, resulting in a two-layer cake that was only about an inch tall and somewhat the consistency of sawdust; once I decided to substitute green food coloring for the red that's called for in a Red Velvet Cake--that cake looked like it was made of spinach). I think I was so preoccupied with the differences in measures that I was having to deal with that I forgot to explore the OTHER difference--the effect of the altitude! My mother always said "Live and learn" (as she choked down chocolate sawdust/spinach velvet cake). Only time will tell whether I learned!
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