- ½ cup (100 g) sugar
- Pinch of kosher salt
- 1 vanilla bean, halved lengthwise
- ½ cup (100 g) silver tequila
- 1 envelope unflavored powdered gelatin (about 2½ tsp.)
- 1 (heaping) cup (200 g) fresh mango pieces (from 1 large ripe mango), puréed until smooth
- 6 Tbsp. (80 g) fresh lemon juice
- 1 tsp. kosher salt
- 2 cups (400 g) sugar, divided
- 3 (150 g) large eggs
- 8 (110 g) large egg yolks
- 6 Tbsp. (85 g) chilled unsalted butter, cut into pieces
- ½ cup (100 g) extra-virgin olive oil
- Vanilla Genoise
- Vanilla Swiss Meringue Buttercream
- Combine sugar, salt, and ½ cup water in a small saucepan; scrape in seeds from vanilla bean and discard pod. Bring to a simmer and cook 2 minutes. Remove from heat and immediately pour in tequila. Strain into a small bowl (you should have about 1 cup). Cover and chill.
- Do Ahead: Soak can be made 3 days ahead. Keep chilled.
- Place ½ cup cold water in a small bowl and sprinkle gelatin evenly over top; chill until ready to use.
- Cook mango purée, lemon juice, salt, and 1½ cups sugar in a medium saucepan over medium-low, stirring to dissolve sugar, until steaming (don’t boil), 5–7 minutes.
- Meanwhile, whisk eggs, egg yolks, and remaining ½ cup sugar in a medium bowl until pale and foamy, about 1 minute.
- Ladle some mango mixture into egg mixture, whisking to combine, then stream egg mixture into remaining mango mixture, whisking constantly. Cook, adjusting heat to keep mixture just under a simmer and stirring constantly with a heatproof rubber spatula, until thick enough to coat spatula and an instant-read thermometer registers 170°, 8–10 minutes. Remove from heat and scrape in softened gelatin; stir to dissolve. Add butter, whisking in a piece at a time, then gradually stream in oil, whisking constantly. Strain curd through a fine-mesh sieve into a medium bowl. Set in a larger bowl partially filled with ice water and stir to cool quickly. You should have about 4½ cups curd. Remove from water and cover with plastic wrap, pressing directly onto surface; chill until set, at least 4 hours.
- Do Ahead: Curd can be made 3 days ahead. Keep chilled.
- Line a 9″-diameter cake pan or springform pan with plastic wrap, pressing into bottom and leaving generous overhang. Fit a 1-piece round of cake into pan, placing bottom side up. Using a pastry brush, dab a quarter of soak across entire surface of cake. Stir chilled mango curd to loosen, then scrape a third over cake and smooth in an even layer with a small offset spatula. Place another round of cake on top of curd, bottom side up, this time using a 2-piece layer. Repeat soaking and filling process. Top with the remaining 2-piece round of cake, bottom side up, and repeat soaking and filling process one more time. Top with remaining 1-piece round of cake, bottom side up, and brush with remaining soak. You should have 4 layers of soaked cake separated by 3 layers of filling. Wrap plastic overhang up and over cake; chill at least 12 hours and up to 2 days to allow mango curd to set and cake to absorb soak.
- To frost, remove plastic from top of cake and invert cake onto a cake plate or platter. Remove pan and plastic. Dollop about 1 cup buttercream over top of cake and smooth across top and down sides, creating a very thin layer. You want to fill in any gaps, adhere any crumbs to the cake, and seal in the fillings (this is called a crumb coat). Chill cake 10 minutes, then scrape remaining frosting on top of cake and spread all over, working down and around sides. Decorate as desired.
- Do Ahead: Cake can be made 2 days ahead. Chill until frosting sets, then cover loosely with plastic wrap. Let sit at room temperature 1–1½ hours before slicing.