My grandma has been making this cake for as long as I can remember. It’s a staple at Christmastime, always displayed on a pretty platter next to the other homemade goodies like fudge and peanut brittle. It has a folk following in our family, as Decker Cake is only ushered out for holidays and the most special occasions (I requested my grandma make a tray for the reception party we had after our wedding). The “cake” is served in bar or square form, and consists of layers of sponge cake, a walnut filling, a pineapple filling, and the whole thing is topped off with a layer of prune butter, then sprinkled with a small piece of crumbled cake. I know what you’re thinking… “Prune butter?!” Just trust me, it’s amazing, and all of the flavors go so well together.
For some reason, Decker Cake, has always seemed to be a massive mystery; no one but my grandma had ever made it. Last December, I called my grandma to ask for the recipe so that I could make it. Like most grandma recipes, there was a list of ingredients and about 10 words, max, of instruction. I called back and asked if I could come over and make it with her, so I could see how she did it. We had a wonderful afternoon baking, and I took a page of notes so that I could recreate the recipe properly.
Decker Cake is rich, so a little bit goes a long way. My grandma often makes a half recipe and assembles it in an 8-inch or 9-inch square pan instead of a full recipe in a 9×13-inch pan. Since the cake is baked in two large half-sheet pans, you need to cut it to fit into the 9×13-inch pan for assembly. When I made it with my grandma, she just cut strips and squares that she could easily move with a spatula, and then fit it into the layers, sort of like Tetris. You can cut larger sections if you have large cake-lifter spatula, or smaller pieces, whatever is manageable for you. She stressed that getting it in one whole piece wasn’t important at all, because of all the layers, and she always cuts and fits her pieces as needed.
This year, I tackled the Decker Cake all on my own, and was thrilled at how it turned out. It’s currently sitting in the freezer, waiting to be sliced up and arranged on various Christmas cookie platters. This was one of my dad’s favorite holiday treats, so I’m especially happy that I can now recreate something that he loved, even if he’s no longer here to enjoy it.
Prepare the Walnut Filling: Place the ground walnuts in a large bowl and set aside. In a small saucepan, combine the sugar, water and butter over medium-high heat, and cook, stirring occasionally, until the sugar is dissolved and it comes to a boil. Remove from the heat and stir in the vanilla extract. Pour the hot syrup over the ground nuts, leaving about ½ cup of the syrup back. Stir together and if still a little dry, add more liquid a bit at a time. You want a moist, spreadable consistency, but you do not want it to be soupy. Set aside.
Prepare the Pineapple Filling: In a small saucepan, combine the crushed pineapple (including the liquid), sugar and cornstarch over low heat. Cook, stirring constantly, until the mixture thickens, about 3 to 5 minutes. Set aside to cool.
Make the Cake: Preheat oven to 350 degrees F. Line two half-sheet pans (13x18-inches) with parchment paper; set aside. In a medium bowl, whisk together the flour and baking powder; set aside.
Using an electric mixer, beat together the shortening and sugar on medium speed until light and fluffy, about 2 minutes. Add the eggs and vanilla extract and mix until completely combined. Reduce the mixer speed to low and add the flour in three additions, alternating with two additions of the warm milk, mixing until completely combined.
Divide the dough between the two baking sheets and use an offset spatula to spread the dough into an even layer on each sheet (the dough will be thick, like cookie dough, and will spread very thin). Bake until the cake springs back when the top is lightly pressed, about 10 to 15 minutes. Remove the pans from the oven and place on wire racks to cool completely.
Assemble the Cake: In a 9x13-inch pan, layer the sponge cake, cutting it as necessary to make a layer fit. Top with the walnut filling, spreading it into an even layer. Top with another layer of cake, again cutting and fitting pieces if need be. Top with the pineapple filling, spreading it into an even layer. Top with the final layer of cake, reserving a small strip of cake. Spread the entire jar of prune butter over the top and crumble the reserved strip of cake over the top. (My grandma mentioned that if you can't spare a strip of cake to crumble on the top, you can also use crushed up Nilla wafers.)
The assembled cake should be stored in the refrigerator and set out at room temperature about 30 minutes before serving. It will keep in the refrigerator covered with plastic wrap and foil for 1 week. This cake also freezes very well, wrapped tightly with plastic wrap and foil for up to 1 month.