This is basically a "German Chocolate Cake," except that the cake part is a different recipe, taken from the 1950 Betty Crocker Cookbook, and the icing recipe is somewhat enhanced, mostly in quantity. You need a total of 7 eggs.
I used to make this as a layer cake, in 3 layers, lining them with parchment paper and all that, but it's a hassle and I found that I would end up eating the layers separately, anyway. Now I make it as a sheet cake, in the largest pyrex pan that I've got, which is almost 10"x15". If I had a larger pan, like a lasagna pan, I'd use that, but you can make do with 9"x13", or you could use multiple smaller pans.
Cake
2 c sifted cake flour
3/4 c cocoa
2 tsp baking powder
1 tsp salt
1 1/2 c milk
1 tsp vanilla extract
2 egg whites
1/2 c sugar
1/4 c shortening (crisco)
1 1/2 c sugar
2 egg yolks
Preheat the oven to 350 F. Start by separating the 2 eggs, putting the whites in the bowl for beating to warm up, retaining the yolks.*
Sift some cake flou; measure 2 cups of it back into the sifter, then add the cocoa, baking powder, and salt to the sifter and sift it all together into a bowl. If you decide to skip this step, I am not responsible for the result.
Make a meringue of the whites by beating them to soft peaks, then slowing adding the 1/2 c sugar while you continue to beat. Remove to a second bowl.
Cream together the shortening and 1 1/2 c sugar. Add the yolks and beat well. Add the flour/cocoa mixture alternately with the milk/vanilla in about 4 steps, mixing thoroughly after each addition. Gently fold in the meringue by hand. Pour into greased baking pan(s). Bake just until a toothpick comes out clean. For the 10"x15" pan, that's 25 minutes. For three 9" round pans, it's less, more like 20 minutes. Be careful not to over bake.
Icing
1 large can evaporated milk
1 1/2 cup sugar
5 egg yolks
4 T butter
1 1/2 c chopped pecans (I usually use roasted, salted pecans)
2 1/4 c grated coconut
1 T vanilla
Combine evaporated milk, sugar, yolks, and butter, in a large saucepan (nonstick is good). Bring to a boil. You can do this on medium-high heat if you stir often, and stir constantly when it's about to come to a boil, as that when it's most like to burn, which is a drag. I use a whisk. Once is boils, start timing 12 minutes of boiling. Stir often, alternating between a whisk and some flat-bottomed wooden spoon and/or heat-resistant silicone spatula, to make sure none of it hangs out too long in one place on the bottom of the pan. By the end of 12 minutes, it will be pretty thick and a light caramel color. Remove from heat; add pecans, coconut, and vanilla. Spread on the cake.
You can, of course, eat some immediately, but it will get better over the course of the next 24 hours. Freezes well.
*Since I use the same KitchenAid mixer bowl for both beating the meringue and mixing the batter, I do the whites first and then transfer them to a holding bowl. I used to beat the whites directly in the second bowl with hand mixer. Your call.