For the cake
3/4 cup skinned pistachio nuts
1 2/3 cups sugar
2 cups cake flour
1 tablespoon baking powder
1/2 teaspoon salt
8 ounces unsalted butter, at room temperature
1/2 cup milk
2 teaspoons vanilla extract
5 eggs, lightly beaten

For the marzipan
8 ounces almond paste
1 1/2 cups confectioners’ sugar
1/4 cup light corn syrup

For the dark ganache glaze
1 pound extra-bittersweet chocolate
1 1/4 cups heavy cream
3/4 cup apricot preserves

Marzipan roses for decoration (optional; see note)