Prepare the Cupcake Pans: Preheat the oven to 170°C (340°F) and line 24 cupcake cases in two 12-hole cupcake tins.
Beat the Wet Ingredients: Add the sunflower oil, extra-large eggs, and white sugar to the bowl of a stand mixer fitted with a whisk attachment. Beat on medium-high speed for about 4 minutes, or until the mixture becomes light and fluffy.
Combine the Dry Ingredients: Sift the cake flour, salt, and baking powder together to remove any lumps and distribute the ingredients evenly.
Make the Batter: Add the sifted flour mixture to the whipped egg mixture and beat on low speed just until combined.
Add the Milk: Combine the whole milk and vanilla bean paste in a jug. With the mixer running on low, slowly pour the milk mixture into the batter. Scrape down the sides of the bowl, then mix again until the batter is smooth and lump-free.
Fill the Cases: Divide the batter between the prepared cupcake cases, filling each approximately two-thirds full. A jug or cookie scoop can be used to make portioning easier.
Bake the Cupcakes: Bake at 170°C (340°F) for 12–15 minutes, or until a skewer inserted into the center of a cupcake comes out clean.
Cool the Cupcakes: Leave the baked cupcakes in their tins for 5 minutes, then transfer them to a cooling rack and allow them to cool completely before filling and decorating.
Prepare the Mango Purée: Peel and slice 200 g of mangoes, then process them in a food processor until smooth. Pass the purée through a fine-mesh sieve to remove any fibrous mango strands.
Cook the Mango Filling: Place the sieved mango purée, lime juice, and superfine sugar in a medium saucepan over medium heat. Cook until the sugar has dissolved and the purée has thickened.
Chill the Purée: Transfer the cooked mango purée to a glass jar and refrigerate until completely cooled and firm enough to pipe.
Prepare the Buttercream: Add the unsalted butter and powdered sugar to a stand mixer fitted with a paddle attachment. Beat at medium speed until the mixture resembles fine breadcrumbs.
Add the Vanilla Mixture: Combine the vanilla bean paste and whole milk in a small jug.
Finish the Buttercream: With the mixer running, slowly pour the milk and vanilla mixture into the butter and sugar mixture. Once all the liquid has been incorporated, increase the speed to high and beat for about 5 minutes, scraping down the sides of the bowl regularly, until the buttercream is light and fluffy. Prepare the Frosting Bag: Transfer the finished vanilla bean buttercream to a piping bag fitted with your chosen nozzle.
Prepare the Mango Topping: Finely dice the remaining 200 g of mango and place it in a small bowl. Add the lime juice and lime zest, then stir gently until the mango is evenly coated.
Core the Cupcakes: Once the cupcakes have cooled completely, use an apple corer to remove the center of each cupcake, creating an opening for the mango filling.
Fill the Centers: Pipe the chilled mango purée into the hollow center of each cupcake.
Pipe the Buttercream: Pipe a circle of vanilla bean buttercream around the outer edge of each cupcake, leaving the filled center open.
Add the Fresh Mango: Spoon the diced, lime-seasoned mango into the open center of each cupcake. Serve and enjoy.
