Black pearl ganache:
6 oz bittersweet (not unsweetened) or semisweet chocolate, chopped
3/4 Cup heavy whipping cream
1 tsp Ground Ginger
1/2 tsp Wasabi Powder
2 Tbsp Black Sesame Seeds
1 Tbsp corn syrup
2 Tbsp (1/4 stick) butter, room temperature
1 Cup water
1/2 Cup sugar
5 Tbsp matchstick-size strips peeled fresh ginger
1 Vanilla Bean, split lengthwise
For the Cake:
2 Cups boiling water
1 Cup unsweetened cocoa powder
2-3/4 Cups all purpose flour
2 tsp baking soda
1/2 tsp baking powder
1/2 tsp salt
2 1/4 Cups sugar
1 Cup (2 sticks) unsalted butter, room temperature
4 large eggs
1 Tbsp Vanilla Extract
Whipped Cream Frosting:
2 Cups chilled heavy whipping cream
1/4 Cup plus 2 Tbsp powdered sugar
1/2 tsp Vanilla Extract
1/2 tsp Ground Ginger
Additional Black Sesame Seeds
For black pearl ganache:
Place chocolate in medium bowl. Bring cream, ginger, and wasabi to boil in small pot. Pour hot cream over chocolate; cover with plastic wrap and let stand 15 minutes. Whisk cream and chocolate until melted and smooth.
Mix sesame seeds and corn syrup in small bowl to coat; stir into chocolate mixture. Let mixture cool to lukewarm. Stir in butter. Cover and let stand at room temperature overnight to set.
For ginger syrup:
Place 1 cup water, sugar, and ginger in small saucepan. Scrape seeds from vanilla bean into pan; add bean. Stir over medium heat until sugar dissolves. Simmer 2 minutes; remove from heat. Let stand at room temperature 1 hour for flavors to blend.
Strain syrup into small bowl. Chop ginger. (Can be prepared 1 day ahead. Cover and refrigerate ginger and syrup separately.)
Preheat oven to 350°F. Butter and flour three 8-inch-diameter cake pans with 2-inch-high sides. Line bottoms of pans with parchment paper.
Whisk 2 cups boiling water, cocoa powder, and reserved chopped ginger in medium heatproof bowl.
Whisk flour, baking soda, baking powder, and salt in large bowl.
Using electric mixer, beat sugar and butter in large bowl until fluffy, about 1 minute. Add eggs 1 at a time, beating until incorporated after each addition. Beat in vanilla extract. Add flour mixture in 4 additions alternately with cocoa mixture in 3 additions, beginning and ending with flour mixture.
Divide batter among prepared cake pans; smooth tops.
Bake cakes until tester inserted into center comes out clean, about 30 minutes. Cool in pans 5 minutes. Turn cakes out onto racks; cool completely. (Cakes can be prepared 1 day ahead. Wrap with plastic wrap and store at room temperature.)
For whipped cream frosting:
Whisk cream in large mixing bowl with an electric mixer. Add sugar, vanilla, and ginger. Beat until stiff peaks form.
Using long serrated knife, trim rounded tops off cakes to create flat surface [so cake will “layer” nicely].
Place 1 cake layer, cut side up, on plate. Brush top with 1/3 cup ginger syrup. Spread half of ganache over top of cake. Place second layer, cut side up, atop first layer. Brush with another 1/3 cup syrup; spread with remaining ganache. Top with third cake layer. Brush with remaining syrup.
Spread sides and top of cake with whipped cream frosting. Sprinkle top with black sesame seeds. Refrigerate until ganache is set, about 4 hours.
Let stand at room temperature 30 minutes before serving.