Before working on Linzertorte, a traditional Austrian cake, we started today's class by preparing a hot milk sponge cake to be used for next week's class. Chef said this type of sponge cake is not that popular anymore, but she recalled seeing descriptions of it in old recipe books in cooking libraries in France. We heated a mixture of whole eggs, sugar and salt over a water bath until it was hot to the touch (110°F), then whipped it until it doubled in volume. To that we added flour and baking powder until just incorporated. Next, we added a mix of milk and butter that we had scalded, and stirred it briefly. The batter was poured out into a parchment-lined sheet and baked. These sheets were then stacked and frozen to be used next week.
On to the main cake. We creamed butter and shortening, icing sugar and flavourings with the paddle until fluffy, then added eggs one at a time. A few teams had problems with the batter splitting, which was solved by turning the mixer to high speed: the increased friction helps to re-emulsify the mixture. To the creamed mixture, we added the dry ingredients: pastry flour, bread crumbs, baking powder, cinnamon and ground nuts. The recipe called for cake crumbs, but Chef didn't have any, so we used about half the amount in bread crumbs by weight. The crumbs add body and help absorb some moisture. During her demo, she decided to omit them completely from her version. As for the nuts, I detected a trace of rancidity in the giant plastic bag we scooped from. It's always better to toast and grind your own nuts but it is time-consuming and probably not practical on a large scale.
We scaled 400 g of batter into 9" cake tins, then spread it evenly with wet hands. A layer of raspberry jam went on top, spread almost to the edges. Then we took a #3 plain tip and piped a lattice and border on top. After an egg wash and a sprinkle of sliced almonds, these were ready to go in the oven.
After they came out of the oven, Chef had an answer to whether or not the crumbs were needed: her lattice topping expanded and almost covered the jam completely. My lattice came out alright, except near the edge, where I had piped a double border because we had batter leftover. 500 g would probably have been the right amount, like it said in the recipe. Chef said this cake is best served during afternoon tea, as it's quite dense and rich. It can be made with different jams and combinations of ground nuts. She also said that after a day or two, the moisture from the jam is absorbed into the cake, keeping it moist. It was pleasantly nutty, with the raspberry providing a nice contrast.