-
1
1.
-
2
To make the buttercream: Stir the sugar and water in a small saucepan over low heat until the sugar dissolves, about 5 minutes.
-
3
Increase the heat to medium and boil, without stirring, until the syrup reaches the soft-ball stage, or 250F on a candy thermometer, about 10 minutes.
-
4
2.
-
5
Meanwhile, beat the egg yolks until pale and thick, about 4 minutes.
-
6
In a slow, steady stream, pour the hot syrup into the eggs, beating continuously as you pour.
-
7
(Do not let the syrup touch the beaters or it will spin into threads.)
-
8
Continue beating until the mixture thickens and cools to room temperature, about 10 minutes.
-
9
3.
-
10
Beat in the butter and shortening, 2 tablespoons at a time, until absorbed.
-
11
Gradually beat in the chocolate.
-
12
Blend in the vanilla, salt, and rum if using.
-
13
Do not add the flavoring too quickly or the buttercream might curdle.
-
14
Chill until of spreading consistency, at least 2 hours or up to 1 week.
-
15
If the buttercream firms too much, return to room temperature before using, about 1 hour.
-
16
4.
-
17
Preheat the oven to 350F.
-
18
Grease the bottoms of several 9-inch round cake pans and dust with flour, tapping out the excess.
-
19
Or grease and flour several large baking sheets and, using a 9-inch saucepan lid or springform pan, mark 9-inch circles on the sheets.
-
20
5.
-
21
To make the batter: Beat the eggs and sugar until thick and creamy, 5 to 10 minutes.
-
22
Add the vanilla and salt.
-
23
Sift the flour over the top and carefully fold it in.
-
24
6.
-
25
Spread about 1/4 cup of the batter evenly over the bottom of the prepared pans or over each circle on the baking sheets.
-
26
7.
-
27
Bake until the edges begin to color, 5 to 7 minutes.
-
28
Loosen with a spatula, invert onto a rack, and let cool.
-
29
Wipe the pans, regrease, dust with flour, and repeat until there are 7 or 8 matching layers.
-
30
8.
-
31
To make the caramel if using: Stir all the caramel ingredients in a small saucepan over low heat until the sugar dissolves, about 5 minutes.
-
32
Stop stirring, increase the heat to medium, and cook, swirling the pan occasionally, until the syrup turns a deep amber color.
-
33
Do not burn.
-
34
9.
-
35
Using a lightly oiled metal spatula, spread all of the caramel evenly over one of the cake layers.
-
36
Let set slightly (do not let it harden), then use an oiled knife to cut just the caramel into 8 to 10 wedges (indicating where the cake will be sliced).
-
37
10.To assemble: Place a cake layer on a serving plate, spread with 1/8-inch thick layer of buttercream, then place a second layer on top.
-
38
Repeat layering the buttercream and cake layers.
-
39
Cover the top of the cake with buttercream.
-
40
If using the caramel layer, place on top of the cake.
-
41
Cover the sides of the cake with buttercream.
-
42
Chill.
-
43
Store in the refrigerator for up to 1 day or in the freezer.
-
44
Let stand at room temperature for at least 30 minutes before serving.
-
45
Oblong Layer Cake: Divide the batter between two 15 1/2-by-10 1/2-inch jelly roll pans and bake.
-
46
After cooling the cakes, cut each lengthwise into 3 equal pieces to make a 6-layer cake.
