This one's pretty involved, but family and guests will love this festive cake
For the Walnut Filling:
1 pound walnuts, ground
1 cup granulated sugar
½ cup water
2 tablespoons butter
¼ teaspoon vanilla extract
For the Pineapple Filling:
1 (20-ounce) can crushed pineapple
½ cup granulated sugar
3 tablespoons cornstarch
For the Topping:
1 (18-ounce) jar prune butter (lekvar)
For the Cake:
3 cups all-purpose flour
1 tablespoon baking powder
1 cup vegetable shortening
1 cup granulated sugar
1 teaspoon vanilla extract
¾ cup warm milk
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.)
7. 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.