Having nothing whatsoever to do with the country of Germany and truly an all-American creation, German chocolate cakes have a reputation for being an indulgently rich dessert. Named for Samuel German, who developed the formula for the dark baking chocolate that would become the original recipe's star ingredient in 1957, this beau idéal of a chocolate cake has been cemented in the annals of food history as an iconic American classic. And no place more than in the Deep South has this cake become a crown jewel of American baking, where its use of (oh so gooey and moist) coconut and pecan filling makes it a regional favorite. This original Passover variety makes for an awesomely moist, rich chocolate cake, and it's gluten-free to boot (giving myself a pat on the back). This recipe also makes use of many ingredients that do not require special kosher-for-Passover certification, such as unsweetened flaked coconut, pecans, cocoa, and Trader Joe's organic coconut milk (basically all the ingredients). Enjoy, y'all, and a happy Passover.
Preheat oven to 350°F. In a medium bowl, sift together the cocoa powder, potato starch, and baking soda. Set aside. In the bowl of a standing mixer, using the paddle attachment*, beat the eggs and sugar until mixture reaches the sabayon/ribbon stage and the mixture is a pale-yellow color, about 1 to 1 1/2 minutes. While continuing to beat, slowly add in the oil in a steady stream. Add the vanilla and mix to combine. Slowly add the dry ingredients and mix until incorporated (do not over-mix). Grease three 8-inch round cake pans with a light coating of oil and line the bottoms with parchment paper. Distribute the batter evenly among the three pans and bake for 18-20 minutes, or until the top is firm (though spongy) and an inserted toothpick comes out clean. Another indication of the cake being ready, is that it should pull away slightly from the sides of the pan. Remove from oven and let cool slightly. Remove from pans while still somewhat warm. (I recommend freezing the cakes prior to frosting for easier handling.)
*Preferred equipment. If you do not have a standing mixer with a paddle attachment for Passover use, you can use a handheld mixer, if necessary.
Preheat oven to 350°F. Spread the coconut on a rimmed baking sheet. Spread pecan halves on another rimmed baking sheet (trying to keep the 30 pecan halves for decoration separate from the 1 1/2 cup needed for the filling). Bake, stirring both the coconut and the pecans every two minutes, for about 10 minutes, or until coconut is golden-brown and pecans are fragrant. Remove from oven and let cool completely. Roughly chop the 1 1/2 cup of pecans once cooled.
Whisk the egg yolks with the coconut milk, sugar, vanilla, and salt in a heavy-duty, nonreactive 4-quart saucepan. Set over medium-high heat and stir almost constantly with a heatproof spatula. When the mixture starts to boil, adjust the heat so that it boils actively but not furiously, and cook, until golden-brown and thickened, about 3-4 minutes. Remove from heat and stir in the toasted coconut and pecans. Let cool completely.
To assemble the cake: put one cake layer on a cake plate. Spread a third of the filling over the top of the cake. Top with second cake layer and spread with half of remaining filling. Top with third cake layer and spread remaining filling over the top and around the perimeter of the cake. The filling/frosting will not completely cover the perimeter of the cake (but that's okay, I think it looks kind of cool that way). Arrange pecan halves in a ring around the edge of and in the center of the cake. Serve at room temperature.