Make the Chocolate Chai Cake:

1. Preheat oven to 325ºF. Butter the bottom and sides of two 4" round, 2" deep cake pans and line bottoms with parchment circles. Dust sides with cocoa and tap out excess.
2. Pour the boiling water over the tea bag in a glass and let steep while preparing the cake batter, for at least 5 minutes.
3. Sift the flour and cocoa into a bowl. Add the salt, baking powder, baking soda, cinnamon, cardamom, cloves, and ginger and whisk together until evenly combined.
4. In a separate bowl, combine the oil, granulated sugar, egg, and sour cream. Whisk together until smooth.
5. Add half of the dry mixture to the wet ingredients and fold in until almost evenly incorporated, with a few streaks of the dry still visible. Squeeze out any liquid soaked up in the tea bag (to ensure you still have 3 oz liquid) and pour brewed tea into batter. Fold in until partially incorporated. Add the remaining dry ingredients and fold everything together just until evenly combined with no dry ingredients visible; lumps are fine.
6. Divide the batter evenly between the two prepared cake pans. Bake in the preheated oven for 40-45 minutes, until a toothpick inserted into the center of each comes out clean or with barely a few small crumbs.
7. Allow cake to cool in pans for 15 minutes, and then turn out onto a wire rack lined with two large squares of plastic wrap. Once cakes have cooled completely, use plastic wrap to wrap tightly until ready to frost. About 1 hour before assembling cake, place wrapped cakes in an airtight zip-top bag and chill in freezer.

Begin the Chai Whipped Cream:

1. Microwave 2 1/8 ounces (1/4 cup) cream in a microwave-safe measuring glass for 15-20 seconds, or just until it begins to boil. Pour over the tea bag in a heat-safe cup and leave to brew, about 5 minutes. About halfway through this time, use a spoon to stir the cream and press the flavor out of the tea bag. Once brewed, transfer to the refrigerator to chill until cold.
2. If possible, chill bowl of stand mixer, or other bowl for beating cream, during this time.

Make the Chai-Infused Chocolate Ganache:

1. Brew another tea bag in 2 1/8 ounces (1/4 cup) cream just as you did for the chai whipped cream above. Set aside after brewing; do not refrigerate.
2. Place the chopped chocolate in a microwave-safe bowl. In a separate, microwave safe measuring glass or bowl, microwave the remaining 6 1/8 ounces cream (3/4 cup) to bring just to a boil, about 45-60 seconds. Pour over the chopped chocolate and add the brewed chai, making sure all of the chocolate is submerged. Let sit for 5 minutes, and then stir until completely smooth. Stir in the sifted confectioner's sugar. Set aside to cool until spreadable, stirring occasionally to promote even cooling.

Finish the Chai Whipped Cream:

1. Once the chai brewed for the whipped cream has cooled completely, remove from refrigerator and sprinkle the gelatin on top. Stir in and let sit for 5 minutes to bloom. Once bloomed, microwave for 5-10 seconds at a time, stirring in between increments, until all of the gelatin has dissolved. Be careful not to let the cream come to a boil during this time. You may need to press on any bits of clumped gelatin with a spoon as you stir until it fully dissolves. Once done, strain through a fine-mesh sieve into a clean container.
2. In (chilled) bowl of stand mixer (or other bowl if using a handheld mixer) beat remaining 8 1/4 ounces (1 cup) heavy cream with vanilla bean seeds until thickened, stopping just before soft peaks form. With mixer speed on low, slowly add sifted confectioner's sugar. Keep on low as you add strained gelatin mixture in a very slow stream. Add spices. Increase speed and beat JUST until stiff peaks form; I usually stop just shy of this point and finish beating with a whisk to prevent overbeating.

Assembly:

1. Place one cake on a rotating cake stand and slice the top off to create a flat surface. Then, slice cake layer in half to create two thinner, even layers. Repeat with second cake.
2. Set first layer on a cardboard cake round on top of cake stand. Using an offset spatula, spread a thin layer of cooled ganache on top, followed by a thin layer of whipped cream. Spread a thin layer of ganache on top of remaining cake layers before stacking. Then, one at a time, stack remaining layers over first, adding a layer of whipped cream over each layer of ganache as you go, until you have a four-tier cake with ganache and whipped cream between each layer. Place in the refrigerator for 30-60 minutes to set (so layers won't slide around when frosting outside of cake).
3. Once set, use an offset spatula to frost top and sides of cake with a thin layer of ganache, making sure to cover the whipped cream between the layers completely to seal it in. Use a bench scraper (or offset spatula) to smooth out the ganache; it doesn't have to be perfect, just somewhat smooth.
4. If ganache on cake feels soft, refrigerate cake until it is firm. Otherwise, continue with cake assembly. If desired, carefully cut off excess cardboard around cake (for cleaner presentation). Then, frost over ganache with whipped cream. Frost top and sides generously, and then use a bench scraper or offset spatula to remove excess cream and smooth top and sides.
5. Decorate cake as desired. I use some of the extra ganache to pipe a ribbon around the top and bottom perimeter of the cake** with a petal piping tip, and decorated with sugar pearls.
6. For easy slicing, refrigerate cake for 1-2 hours to set whipped cream and ganache before slicing. Slice with a warm, dry knife. Store leftover cake in an airtight container in the refrigerator and bring to room temperature before serving.