French Butter Cake

When I tried my hand at gâteau Breton by baking five existing recipes, I quickly learned that there are plenty of ways to go wrong. One cake, made with buckwheat flour (an ancient tradition from the days when wheat flour was unavailable in Brittany), was dry enough for a colleague to liken it to “compressed sawdust.” The center of another was so wet and gummy that folks were convinced it included gooey marzipan. As for the fillings, most tasted flat and were thin and runny; spreading them evenly over the sticky batter proved to be quite a challenge. I wanted a cake with a crumb to rival the very best I had enjoyed in France, along with a lively filling with a workable consistency.

Most modern recipes call for four main ingredients: all-purpose flour, salted butter, sugar, and egg yolks. (Since the test kitchen almost exclusively uses unsalted butter for baking, I would investigate later whether salted butter was worth a special purchase.) I used one of the better recipes from my first round of testing as a starting point. It was pleasantly dense but a little too wet and greasy, so I spent a few afternoons in the test kitchen, baking gâteau after gâteau and slowly increasing the amount of dry ingredients and decreasing the amount of butter until I got a cake I liked.

I also examined the technique. Most recipes call for creaming the butter and sugar before incorporating the yolks and flour, and some specify upwards of 10 minutes of creaming. But extensive creaming incorporated too much air into the batter and resulted in a light, fluffy crumb—just the opposite of what I wanted. Ultimately, I landed on creaming two sticks of butter with a little less than 1 cup of sugar in a stand mixer for only 3 minutes, adding 5 yolks one at a time, and finally mixing in 2 cups of flour. This produced an ultrathick batter that baked up with the trademark firm yet tender crumb that I was after.

With the cake nailed down, I dug deeper into the butter issue. Bretons insist that their local butter made with sea salt is key to this cake, so I arranged a head-to-head comparison of cake made with the test kitchen’s favorite salted butter, Lurpak (a cultured butter from Denmark), and cake made with our favorite unsalted sticks, from Land O’Lakes (with some salt stirred into the batter to compensate). Not surprisingly, tasters found that the European butter delivered a slightly more complex cake, but in the end I decided that the difference wasn’t enough to warrant the extra cost or trip to the market.

I did, however, want to explore other ways to add complexity. In France, liquor is often used as a flavor enhancer for this cake, so why not add some to mine? I experimented with kirsch and Calvados before finally settling on dark rum for its rich caramel notes. I also added vanilla extract for even more depth.

I’d produced a rich, flavorful cake with just the right dense texture. Now it was time to address the filling. A prune puree is traditional, and while I did end up developing a prune variation, I preferred to showcase a version with a brighter, bolder filling. I’d seen recipes featuring chocolate, date, or apricot fillings, and apricot seemed like the ideal foil to my buttery cake.

Unfortunately, store-bought apricot jam was too sweet and dull; plus, it was too thin and runny to work well as a filling. You see, when constructing this cake, you first spread half the thick batter in the bottom of a buttered cake pan, and then you layer on the filling before finally spreading the rest of the batter on top and baking the cake. If the filling is too thin, it’ll either get picked up and mixed in with the batter or leak from the sides of the cake as it bakes, creating a real mess.

I thought that reducing the jam might concentrate its flavor and give me the consistency I wanted, but ultimately I decided to craft my own filling from dried apricots so that I could achieve the exact flavor and consistency I wanted.

Too bad my first batch didn’t taste very good. I had made the puree with dried Turkish apricots, and they just didn’t have enough oomph. Using dried Californian apricots remedied this weakness in a hurry: Their concentrated sweet-tart flavor delivered a bright, fruity zing. I chopped up the apricots, tossed them into a blender with enough water to engage the blade, and whizzed them until smooth. After cooking the puree in a skillet with sugar until it thickened and darkened slightly, I squeezed in a bit of fresh lemon juice. Now I had a thick, fruity puree to highlight the rich, buttery cake.

To make the assembly of the cake foolproof, I experimented with what a fellow test cook called a “jam dam,” a lip of batter at the edge of the pan designed to hold the filling in place and keep it from oozing out the sides of the cake during baking. It worked well enough in that regard but did little to keep the jam from mixing with the cake batter. Ultimately, I solved the problem with a bakery trick: quickly chilling the first layer of batter by sliding the cake pan into the freezer. Given the high concentration of butter in this cake, just 10 minutes of chilling did the trick: The batter became so firm that it didn’t budge when I spooned on the apricot puree. Putting the pan back into the freezer for 10 minutes once the jam layer was on ensured that everything stayed put when the remaining batter was added.

All that was left to do was pretty up the cake with a simple egg wash and decoration. Here, I didn’t deviate at all from tradition. I first brushed the cake with an egg yolk beaten with a teaspoon of water (this would give it a slight sheen) and then gently dragged the tines of a fork across the cake’s surface in a crisscrossing diamond pattern. This branded my dessert as a classic gâteau Breton and was the final step in ensuring that my beautiful, buttery cake held true to its roots.