Classic Chiffon Cake with Vanilla Chantilly

Ingredients

• For the cake:
• About 8 ounces egg white, plus or minus 1/2 ounce, from 6 to 8 large eggs
• 10 ounces plain or toasted sugar
• 3/4 ounce vanilla extract
• 3/4 ounce fresh lemon juice
• 1/2 teaspoon Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
• 2 teaspoons baking powder
• About 4 ounces egg yolk, plus or minus 1/2 ounce from 6 to 8 large eggs
• 4 ounces neutral oil, such as safflower
• 6 ounces cold seltzer or club soda, not tonic water
• 9 ounces all-purpose flour, such as Gold Medal
• To Serve:
• 5 ounces plain or toasted sugar
• Heaping 1/8 teaspoon Diamond Crystal kosher salt, or more to taste; for table salt, use about half as much by volume or the same weight
• 16 ounces heavy cream
• 2 1/2 teaspoons vanilla extract
• Fresh fruit, sprinkles, crystallized violets, or other garnishes, as desired

Directions

1. For the Cake: Move an oven rack to the lower-middle spot and heat the oven to 350 degrees F. In the bowl of a stand mixer fitted with the whisk attachment, add the egg whites, sugar, and vanilla extract. Beat on low speed for about 1 minute to break everything up, then raise the speed to medium-low, 4 on a KitchenAid, and whip for 3 minutes; at this point, the whites should look dark and thick.
2. While the mixer is running, add the lemon juice and salt. Right away, turn the speed up to medium, 6 on a KitchenAid, and whip for 3 minutes more; the mixture will look light and bubbly, though still loose. Add the baking powder, increase the speed to medium-high, 8 on a KitchenAid, and keep whipping until the meringue turns shiny, white, and thick enough to show the whisk’s trails, while still being fairly fluid. Depending on your mixer and how fresh the whites are, this may take 1 to 3 minutes.
3. In a large bowl, whisk together the egg yolks, oil, club soda, and all-purpose flour until the mixture is smooth. Add a third of the meringue to the yolk mixture and whisk gently until it looks even and smooth. Add the rest of the meringue, then use a flexible spatula to fold just until the batter is fully combined and the color is consistent. Stop as soon as you get there; this is not the moment to overmix.
4. Transfer the delicate batter to a 10-inch aluminum tube pan, leaving it completely unbuttered and ungreased and avoiding nonstick, or divide it between two 8- by 3-inch anodized aluminum cake pans, without parchment and without using shallow pans. Bake until the cake has risen, turned golden blonde, and feels set when touched, about 55 minutes for a 10-inch tube pan or 40 minutes for two 8-inch layers.
5. Invert the hot pan or pans and let the cake cool until there is no warmth left at all, at least 2 hours. Run an offset spatula around the cake’s edges to release it. If using a tube pan, lift out the center piece and then work the spatula underneath the cake too. For the 8-inch cakes, set each pan on its side, slip an offset spatula between the cake and the pan wall, and gently tug to free the cake from the base; turn the pan as you go until you have released it all the way around. Move on right away, since the cakes can dry out once exposed to the air.
6. To Serve: Add the sugar, salt, cream, and vanilla to the bowl of a stand mixer fitted with the whip attachment. Mix on low for a minute so the sugar can begin dissolving, then whip on medium-high until the cream stands in stiff peaks, about 4 minutes. Spread it over the chiffon as frosting, or spoon it beside individual slices with fresh fruit, sprinkles, candied flowers, or any toppings you prefer. If frosted chiffon is wrapped tightly in plastic, it can be refrigerated up to 24 hours; bring it back to room temperature before serving.