The Bojon Gourmet

Make the cake:
2 Position a rack in the lower third of the oven and preheat to 350ºLine a 6" round cake pan with 2" high sides with a round of parchment paper. Cut a 4-5" wide strip of parchment paper that's longer than the circumference of the pan and use it to make a collar around the inside of the pan.
3 Place a strainer over a medium bowl and add the almond, oat, sweet rice and millet flours along with the baking soda, cinnamon, cardamom and salt. Sift the dry ingredients into the bowl, adding back in any almond or bran bits that get caught.
4 Combine the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed until light and fluffy, 3-5 minutes, scraping down the sides of the bowl a few times. Beat in the egg yolks and vanilla. With the mixer on low, beat in a third of the flour mixture until combined. Beat in half of the persimmon pulp until combined. Repeat until you've added everything. The mixture may look grainy and that's ok.
5 In a separate, clean bowl, use a whisk to whip the egg whites until they hold firm peaks when the whisk is lifted out of the bowl. (Hint: this is easier if they're at room temperature. You can also do this in a clean bowl for your stand mixer with the whisk attachment.)
6 As soon as the whites are whipped, stir a third of them into the cake batter. Gently fold in the remaining egg whites until no streaks remain.
7 Scrape the cake batter into the prepared cake pan (don't forget the parchment collar if using a 6" pan!). Bake the cake until a toothpick inserted near the center comes out clean, 60-75 minutes for a 6" cake (less time for an 8" pan). Let the cake cool completely, 2-3 hours.
8 When the cake is cool, us a small offset spatula or butter knife to loosen the edges and bottom from the pan. Invert it into your hand, and pry off the pan. Remove the parchment and discard. 
9 Place the cake upright on a board, plate, or cake stand (if you have one that rotates, bonus points!). Use a large, serrated knife to trim the top of the cake flat. Mark the cake horizontally into even thirds. With your palm on the top of the cake and the knife held parallel to the work surface, use a sawing motion to cut the cake as you rotate it, taking care to make the layer as even as possible. Repeat with the second layer.
Make the frosting:
12 In the bowl of a stand mixer fitted with the paddle attachment, whip together the cream cheese, butter, powdered sugar, vanilla seeds, and salt on medium speed until light and fluffy. Be careful not to overbeat, or the mixture could break and become grainy or liquidy. Add the bourbon and beat to incorporate. (Mine always become slightly grainy at this point due to the low amount of powdered sugar, but I find that preferable to being too sweet.) The frosting can be covered and kept at cool room temperature for up to a few hours.
Prepare the fuyus:
15 Slice the tops off the fuyus and cut them into an even dice about 1/4" square or a little larger. Place in a small bowl and toss with a squeeze of lemon juice to keep it from oxidizing.
Assemble the cake:
18 Place the bottom cake layer on a fresh round of parchment or a 6" cake board. Lay the other layers on a clean surface. Divide the frosting between the three layers. Starting with the bottom layer, smooth the frosting over the surface, taking it almost to the edge. Top with about a quarter of the diced persimmon, and press the persimmons into the frosting. Top with a second cake layer. Repeat this process, using the remaining half of the diced persimmon to top the cake.
19 Serve immediately, or, for the cleanest slices, chill the cake at least 1 hour. The cake is best at room temperature when the butter in the cake and frosting has softened, so let individual slices come to room temperature before enjoying.
20 The cake is best on the day of baking, but it will keep refrigerated (ideally in a cake dome or large, inverted containefor up to a few days.