Coconut Tres Leches

Preparation

1. Cake

   Step 1

   Place a rack in middle of oven and preheat to 350°. Separate yolks from 7 large eggs over a small bowl to catch egg whites. Place yolks in the bowl of a stand mixer. Add 2 tsp. vanilla extract and ½ cup (100 g) granulated sugar and fit bowl onto stand mixer. Beat with whisk attachment on medium-high speed until very light and voluminous and mixture leaves a very slowly dissolving ribbon when drizzled back onto itself, about 3 minutes. Rub a small dab between your fingers—it should be grit-free (this means all the sugar is dissolved); beat another minute or so if needed. Scrape yolk mixture into a large wide bowl.

   Step 2

   Thoroughly wash and dry whisk and mixer bowl, then beat egg whites, 1 tsp. cream of tartar, and remaining ½ cup (100 g) granulated sugar on medium-high until meringue is glossy and forms medium peaks, about 4 minutes.

   Step 3

   Using a large rubber spatula, gently fold half of the meringue into yolk mixture (err on the side of mixing less; it’s okay if there are quite a few large streaks of egg white). Sift ¾ cup plus 2 Tbsp. (108 g) all-purpose flour over batter (make sure to sift all over the surface rather than a heap in the center) and fold gently, making sure to scrape sides and bottom of bowl well. Fold in remaining meringue, followed by remaining ¾ cup plus 2 Tbsp. (108 g) all-purpose flour, sifting on top as before (be careful not to overmix or batter will collapse; some streaks are okay, but avoid large lumps or pockets of dry flour).

   Step 4

   Scrape batter into a metal 13x9" baking pan (no need to grease—batter will rise higher in an ungreased pan) and gently spread into an even layer with a large offset spatula, making sure to work into corners. Bake cake until top is golden and center springs back when gently pressed, 25–30 minutes. Let cake cool in pan, about 1 hour.

   Step 5

   Using a chopstick, poke holes into cake, spacing ½" apart and wiggling chopstick gently to widen holes and reach bottom of pan.

2. Soak and assembly

   Step 6

   Heat one 3"-long cinnamon stick, one 13.5-oz. can unsweetened coconut milk, 2 cups whole milk, 2 cups heavy cream, 1 cup (200 g) granulated sugar, and 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt in a medium saucepan over medium-low, stirring occasionally, until sugar is dissolved and liquid is steaming, 7–9 minutes.

   Step 7

   Gradually pour 6 cups coconut milk mixture over cake (it may look like too much, but it will all soak in eventually.) Let cake sit, occasionally tilting pan to redistribute any liquid pooling on the surface, until most of liquid is absorbed, about 1½ hours.

   Step 8

   Remove any pieces of cinnamon stick from cake and discard. Wrap cake tightly and chill until cold, at least 3 hours. Transfer leftover coconut mixture in saucepan to an airtight container; cover and chill.

   Step 9

   Just before serving, stir together 1 cup jam or preserves (such as strawberry, guava, or pineapple) and 2 tsp. fresh lemon juice in a small bowl. Using an offset spatula or spoon, spread jam evenly over entire top of cake.

   Step 10

   Using an electric mixer on medium-high speed, beat 1 tsp. vanilla extract, remaining 2 cups heavy cream, 2 Tbsp. (25 g) granulated sugar, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a medium bowl until soft peaks form, about 4 minutes. Spread whipped cream evenly over jam layer on top of cake.

   Step 11

   Scatter 1 cup toasted unsweetened coconut flakes over whipped cream. Cut cake into 16 pieces and serve with reserved soak for pouring around each slice.

   Do ahead: Cake can be baked and soaked 1 day ahead. Keep chilled. Top with jam, whipped cream, and coconut flakes just before serving.