1Preheat the oven to 350 degrees F. Grease and flour two 8-inch round cake pans.
2Cream the shortening with the 1 cup sugar. Add 1 egg and beat until blended. Sift the 1-3/4 cups flour together with the baking powder and 1/8 teaspoon salt. Add to the creamed mixture alternately with the milk. Stir in the vanilla. Divide the batter between the cake tins.
3Bake for 20 minutes or until a tester inserted near the center of the cake comes out clean. Cool in the pans for 10 minutes, then turn out onto wire racks to finish cooling.
This is a very moist, delicate cake, make sure you remove from pans after 10 min, I run a knife around the edges to loosen.
4To make custard:
Combine the flour with the sugar in a small saucepan. Add the egg, milk, and salt. Cook over low heat, stirring constantly, until the filling is smooth and thick. Stir in the vanilla. Chill in the refrigerator.
5To assemble, spread the filling between the cooled cake layers and top with the frosting.
In a 1-quart saucepan, melt 3 tablespoons butter and the chocolate over low heat, stirring occasionally.
Meanwhile, in 1-cup glass measuring cup, microwave the water uncovered on High 15 to 30 seconds or until hot. Remove chocolate mixture from heat. Stir in the powdered sugar and 3/4 teaspoon vanilla. Stir in 3 tablespoons hot water. Stir in additional water, 1 teaspoon at a time, until icing is smooth and thin enough to spread.
I want to add a note here..if you are unfamiliar with this frosting, it is a strong bittersweet chocolate flavor..the classical frosting for on this type of cake. I am thinking you could add more sugar, and then thin down some more with a bit more water, to get a sweeter frosting. I like it the way it is, but have just a sliver, as it is rich..Sometimes my Gram would just use a store bought frosting, heat it up in the microwave, and pour it on..there are many options.