Butter three 8-inch round cake pans; line the bottom of each pan with a round of parchment or waxed paper and butter the paper.
Spread out the pistachios in a baking pan and toast in the oven for 7 to 10 minutes, or until lightly colored.
Transfer to a dish and let cool completely; finely chop the pistachios and set 1/4 cup aside for decoration.
Put the remaining 1/2 cup pistachios in a food processor.
Add the sugar and pulse just enough to grind them finely.
Pour into a large mixing bowl and add the flour, baking powder, and salt.
Blend with the mixer on low for 30 seconds; add the butter, milk, and vanilla and, with the mixer on low, beat until completely incorporated.
Raise the speed to medium and beat until light and fluffy, 2 to 3 minutes.
Add the beaten eggs in 2 or 3 additions, scraping down the sides of the bowl well and mixing only long enough to blend after each addition.
Divide the batter among the 3 prepared pans.
Bake for about 25 minutes, or until a cake tester or wooden toothpick inserted in the center comes out clean.
Allow the layers to cool in the pans for 10 minutes.
Turn out onto wire racks, carefully peel off the paper liners, and let cool completely.
MAKE THE MARZIPAN:.
Crumble the almond paste into a large mixing bowl.
Use an electric mixer on low speed to soften the almond paste.
Add the confectioners’ sugar and corn syrup and beat until smooth.
Wrap well in plastic so it doesn’t dry out, and allow to rest at room temperature for 1 to 2 hours before rolling out.
MAKE THE DARK CHOCOLATE GANACHE:.
Chop the chocolate coarsely and put it in a heatproof bowl.
Bring the cream to a bare simmer & pour the hot cream over the chocolate and let stand for 5 minutes.
Whisk until smooth and use the glaze soon after making so that it doesn’t set.
ASSEMBLE THE CAKE:.
Roll out a third of the marzipan on a work surface dusted with a little confectioners’ sugar to about 1/8-inch thickness.
Set one of the cake pans upside down on the marzipan and trim around it with a small knife to make an 8-inch round.
Repeat two more times with the remaining marzipan.
Save all your scraps to make roses for decoration, if you like.
Place one cake layer on a cake board, flat side up.
Spread 1/4 cup of the preserves evenly over the top, leaving a 1/4-inch margin all around.
Place one marzipan round on top of the preserves and spread 1/3 cup of the Dark Ganache Glaze over the marzipan so that it completely covers the surface.
Repeat with the second cake layer, adding more preserves, another round of marzipan, and more ganache glaze.
Top the cake with the third layer.
Spread the last of the apricot preserves over the top of the cake and cover it with the last round of marzipan.
Place the cake on a wire cooling rack that is nesting in a baking pan.
Pour the remaining ganache glaze over the cake, in several additions, spreading to coat the top and sides.
Allow the ganache to set.
Garnish the cake with the reserved chopped toasted pistachio nuts and a single marzipan rose or several smaller roses.
TO MAKE THE MARZIPAN ROSES:.
First, tint the marzipan, if desired, by kneading in a tiny amount of paste food coloring, dabbing just a small bit onto the marzipan with the tip of a toothpick.
Flatten the tinted marzipan into a disk and roll out on a work surface dusted with confectioners’ sugar or between 2 sheets of waxed paper to a sheet 1/8 inch thick.
With a 1 1/2-inch round cookie cutter, cut out 8 or 9 circles.
Cover all the marzipan you are not using immediately with plastic wrap so it doesn’t dry out.
Roll one piece of marzipan into a ball the size of a marble and pinch with your fingers to shape into a cone about 1 to 1 1/4 inches high, tapering to a fine point at the top.
Take another round of marzipan and wrap it like a petal around the cone, pinching it at the bottom to adhere and at the top to thin and ruffle slightly like a flower.
Repeat with the remaining petals overlapping slightly as you work your way around. If necessary, use a little water to help glue the marzipan in place.
*Some Prep Tips:.
The cake itself was baked a few days in advance, flash-froze them, wrapped each layer in three sheets of plastic wrap, and decorated it, still frozen. This made them very easy to maneuver, and saved us from the chaos that would be baking and decorating in one session. Wrapped well, you can freeze cakes for up to a month and nobody would ever know upon tasting the final product.