Heat the oven to 325 °F, position a roasting pan on the lower-third rack, and bring a kettle of water to a boil. The roasting pan must have enough room around the springform pan to hold the water bath.

Coat a 9-inch springform pan with nonstick spray, fit parchment over its base, and wrap its exterior bottom and sides with two layers of foil. Keep the foil intact and raised along the sides to help block water from reaching the seams.

Beat the cream cheese until creamy, then mix in the sugar and salt for 2 minutes, scraping the bowl as needed. The mixture should look even, with no firm cream cheese pieces remaining.

Blend in the eggs individually, followed by the sour cream, whipping cream, and vanilla, then transfer the batter to the prepared pan. Stop once the batter looks smooth rather than continuing to whip air into it.

Set the springform inside the roasting pan, carefully add boiling water to a depth of about 1 inch around it, and bake for 45 minutes. The cheesecake should feel set to a gentle touch and should not jiggle.

Lift the cheesecake pan out of the water bath, cool it on a rack for at least an hour, then freeze it completely in its pan. Allow several hours or overnight for a firm disk that can be handled without bending.

Raise the oven temperature to 350 °F and grease and flour two 9-inch round metal pans, or coat them with baking spray containing flour. Cover the pan corners as well as the bases to help the cakes release cleanly.

Whisk the flour, sugar, cocoa, baking soda, and salt together, then add the eggs, oil, buttermilk, coloring, vanilla, and vinegar. The dry mixture should have an even cocoa tint before the wet ingredients go in.

Mix on medium-low for 1 minute, scrape the bowl’s sides and bottom, then beat on high for 2 minutes. The finished batter should look evenly colored without dry pockets underneath.

Divide the batter equally between the pans and bake for 30 to 35 minutes. A toothpick inserted into the middle should carry moist crumbs rather than wet batter.

Cool the cakes in their pans on a rack for 10 minutes, loosen their edges with a knife, and turn them onto racks to finish cooling. The layers must feel completely cool before assembly so they don’t soften the filling or frosting.

Combine the sifted powdered sugar, softened cream cheese, butter, and vanilla in a large bowl and beat on medium-high just until blended. Stop when the frosting looks creamy and spreads smoothly without visible lumps.

Center one cake round on a platter, then release the frozen cheesecake from its springform ring and base, using a knife beneath the parchment to loosen it. Peel away all the paper while the cheesecake is still firm.

Compare the cheesecake diameter with the cake rounds and, if necessary, shave its perimeter on a cutting board before stacking it between the cakes. The edges should line up, with no frosting between the layers because the cheesecake supplies the filling.

Spread a thin coat of frosting over the assembled cake with a long, narrow spatula, wiping the blade clean before taking more frosting, then refrigerate for 30 minutes. Visible crumbs are fine in this first coat, which should feel set before the final frosting goes on.

Spoon frosting onto the chilled cake’s top and spread it outward and down the sides, then decorate as desired and keep refrigerated. The set crumb coat helps the outer frosting stay white, and optional white chocolate shavings add a delicate finish.