Heat the oven to 315°F.
Lightly butter a 8” x 3” round cake pan and line the bottom with parchment paper. Set aside.
In a double boiler, stir together the cream cheese, butter, and milk until the cream cheese melts and everything is smooth and incorporated. Remove from the heat and stir in 1/4 cup sugar and lemon juice until smooth. Let cool completely, stirring to help cool faster.
While the cream cheese mixture is cooling, separate the eggs, putting the whites in the bowl of a stand mixer. Whip the egg whites with the cream of tartar until frothy and pale, adding in the remaining 1/4 cup of sugar in bit at a time until the whites are whipped into a glossy thick soft peak meringue – one that holds its shape, with a beak that folds over on itself. Be careful not to over whip.
When the cream cheese is cool, sift in the flour and cornstarch and whisk until throughly combined. Whisk in the egg yolks until smooth and combined.
Add 1/3 of the whipped egg whites to the yolks and using a whisk, gently incorporate. Add another 1/3 of the whites and whisk again, being carefully not to deflate. Transfer the egg yolk mixture to the remaining egg whites. Whisk together and then use a spatula to fold together.
Pour the batter into the prepared cake pan – it should come up almost to the top of the pan, about 1/4 inch from the top. Tap the pan against the counter to release any air bubbles.
Place the cake pan in the roasting pan and place in the oven. Carefully add hot water to the roasting pan so that it comes about 1/2 way up the cake pan. Bake for 1 hour and 20 minutes. The top should be lightly golden. Open the oven door slightly open to let cool gently for 1 hour. The idea is to let the cake cool very gradually so it doesn’t crack.
While the cake is cooling, make a stencil for Totoro’s belly by taking a sheet of paper and cutting out a curved belly. Make Totoro’s eyes by melting down the white chocolate and piping two eyeball whites on parchment paper. Let harden, then flip and pipe on the eyeballs with melted dark chocolate. Pipe out an oval for his nose and six lines for whiskers. Pipe out five open triangles for his chest hairs. Let cool completely on the parchment paper.
The cake will have natural shrunk from the sides and should be cool enough to touch. Use a cutting board (or your hands) to invert and remove from the pan. Peel off the parchment if desired. Flip back right side up and place on your serving dish. It should be soft, fluffy, and jiggly while it’s still warm.
Place the stencil over the cake and give Totoro a generous dusting of icing sugar to create his belly. Add his eyeballs, nose, whiskers, and chest hairs. Enjoy!