I was never much of a science lover in high school and the lone science class I took in college was Photographic Astronomy (which had the novel attraction of meeting at 11 o’clock at night). The irony of this seeming disinterest in the sciences is that I adore baking. There are a few desserts you can bake without paying attention to the laws of science (blueberry buckle comes to mind but it’s one of the few desserts you can just throw together and it always seems to work). In general baking requires the combination of specific ingredients in such a way so that they meld together with one another causing a reaction or reactions which help to create the desired end result–a risen souffle, an ethereally light angel food cake, smooth creamy custard, a crisp cookie or a soft chewy cookie. It all comes down to the science of how things go together*, including Lemon Sponge Custard.
I did not grow up eating lemon sponge custard, though I wish I had. Instead I discovered it sometime after college when I wanted to shift gears from being a chef to working as a food stylist. Changing careers to a field most people have not even heard of is not easy, so I made many attempts at things which I thought would bring me closer to my goal of food styling. Some of these attempts worked while others did not. One of my plans was to apply for a job as a freelance test kitchen assistant because before any recipe was photographed for a magazine the recipe first had to be tested. My friend Nina suggested I send the head of one of the test kitchens some of my recipes, which were in truth her recipes. This did not get me the job I wanted (though I later did work briefly as a freelancer in another test kitchen) however more fortuitously it introduced me to a dessert I now count among my favorites.
Lemon sponge custard is neither cake nor custard, but some happy amalgamation of both. There are recipes for sponge puddings or sponge custards dating back to the 1800s. The scientific explanation for what happens when you add a large amount of milk to eggs, sugar and flour is that the batter separates as it bakes creating a custard layer on the bottom and a sponge cake on the top. Similar to many custards, you bake this recipe in a bain marie which is simply a French term meaning you cook the food in one vessel by placing it in another vessel containing hot water. The technique was supposedly named after Mary the sister of Moses, who is said to have written a book of alchemical recipes many thousands of years ago. Whether you know the science of this recipe or not the results are the same. You start out with one batter and end up with two different desserts in one, a type of presto-change-o abracadabra cooking magic which happens as it bakes.
Personally I love to cook lemon sponge custard in individual glass custard cups so you can see the different layers, but any custard cup will work. Over the years I’ve collected many custard cups since they are ideal not only for lemon sponge custard, but also as olive pit spittoons and as micro hot fudge sundaes bowls.
I prefer my lemon desserts tart so I’ve boosted the amount of lemon juice and zest called for. I also love making this with local eggs from the farmer’s market which always seem to be a more intense yellow than the ones from the supermarket. They don’t seem to change the taste–it’s a visual thing.
Lemon Sponge Custard
3 eggs, seperated
pinch of salt
2 Tablespoons of unsalted butter, softened
3/4 cup sugar
grated zest of 2 large lemons**
5-7 Tablespoons lemon juice
4 tablespoons flour
1 1/2 cups milk
Put a large kettle on to boil, preheat oven to 350ºF, and set six custard cups in a 9″ x 13″ pan. Beat the egg whites with salt until stiff peaks form. In another bowl cream sugar and butter together, then add the egg yolks and beat some more. Sprinkle in the flour, lemon zest and lemon juice, mixing until everything is combined. Pour in milk and gently whisk together. Fold in egg whites, stirring until nearly all streaks of white are gone. Pour batter into custard cups and set pan on edge of oven rack. Carefully holding onto the pan pour boiling water around the custard cups. You want at least 3/4″ of water. If you have enough water in your kettle you may pour it as high as half way up the sides of the custard cups. Gently slide the pan fully onto the shelf and bake for 38-45 minutes or until the tops are lightly browned. Be careful removing the ban marie pan from the oven. You don’t want to slop any of the hot water into the sponge custards. Likewise be careful removing the custard cups onto a dish towel or cooling rack as the cups are quite hot. Let cool at least 30 minutes. You may serve these either slightly warm or when they are all the way cooled you may put them in the fridge and serve cold. Delicious either way.
* If you want to read about the science of cooking I recommend Shirley Corriher’s books. She’s a biochemist with an astonishing wealth of knowledge about the why’s and why nots of cooking. Harold McGee is another great writer about the science of cooking.
**For decades I’ve used a microplane from Lee Valley Tools. They were one of the first companies to realize a secondary use for an existing tool. There are other companies who make micro planes, including ones with handles. I use my micoplane for three things. Zesting citrus, turning a chunk of Parmigiano Reggiano into a cloud of grated cheese, and for when I want a very fine dusting of chocolate for crêpes or to decorate a cake with.