Preheat the oven to 350F (175C). Prepare a 12x18-inch rimmed baking sheet pan by spritzing with vegetable oil and lining with parchment paper cut to size.
In a small bowl, mix the soy milk with the apple cider vinegar and set aside to thicken.
In a small bowl, whisk the aquafaba until foamy and light, about 1 minute, and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, vegetable oil, and sugar until creamy and blended well. Add the foamy aquafaba, vanilla extract and vanilla beat paste, mixing until combined.
In a large bowl, whisk together the cake flour, baking powder, baking soda and salt.
With the mixer on low speed, alternate between adding the flour mixture and the soy milk mixture, beginning and ending with the flour mixture, until just combined and a cake batter forms. Do not overmix. Use a spatula to fold in any stray flour lumps.
Bake the cake for 22-25 minutes, until edges are lightly browned and the top is golden in colour. Let cool completely on wire rack.
Make The Milk Tea Cake Soak
In a small saucepan set to medium heat, combine the soy milk and granulated sugar, stirring until sugar has dissolved. Remove from heat and add the earl grey tea leaves, allowing them to steep into the hot milk for about 4-5 minutes. Strain the milk tea through a fine mesh sieve to remove the tea leaves. Let cool completely before using.
Make The Buttercream
In the bowl of a stand mixer fitted with the whisk attachment, whip the aqua faba on low speed to foam up, about two minutes. Add the cream of tartar.
Turn the mixer up to high speed and beat until medium stiff peaks appear, 5-10 minutes or more. Begin adding the sugars, one teaspoon at a time, until incorporated.
Once the meringue reaches stiff peaks, begin adding the butter, one tablespoon at a time until incorporated.
Whip the mixture on high speed until creamy and luscious. Add the vanilla and vanilla bean paste and mix to combine.
Swap out the whisk attachment for the paddle attachment and whip on medium speed to deflate air bubbles, if desired.
Assemble The Cake
Line the sphere pan or large bowl with two long pieces of cling wrap so the cling wrap overhangs the bowl.
Place a dollop of buttercream into the bowl and cut out a piece of cake to nestle on top. Using a pastry brush or spoon, add the milk tea soak to the cake.
Once the milk tea soaks in, add a thin layer of raspberry jam.
Add a thick layer of buttercream, using an offset spatula to spread to the edges of the bowl. Nestle fresh raspberries into the buttercream.
Add another layer of cake cut to size, and continue to layer and build until you've reached the top of the bowl, with a final layer of cake. Cover the cake with the clingwrap overhang and chill in the fridge for 4 hours until firm, or overnight!
Remove the bowl from the fridge. Unwrap the overhang and place a cake board or plate on top of the bowl. Deftly invert the cake bombe onto the cake board.
Colour the remaining buttercream with food gel colouring, if desired. Frost the entire exterior of the cake bombe with a thin layer of buttercream; chill until set, about 20 minutes in the fridge.
Frost the cake bombe with a final coat of buttercream, using a cake bench scraper of offset spatula to smooth it. Fill a piping bag fitted with a #70 large leaf tip or #104 petal tip. Add ruffles and squiggles to your liking. Add fresh berries, edible flower petals and herbs, if desired! Top with a strawberry, raspberry or a stemmed cherry!
Refrigerate until ready to serve and enjoy!
notes
Cake is best eaten the day it was made, however it will last up to 3 days, well-covered, in the fridge!