Instructions

• 1 Preheat oven to 350°F and line a 12-count cupcake tin with paper liners. Set aside.
• 2 For the custard: Combine milk, cream, 1/6 cup sugar, and salt in a medium-sized saucepan over medium heat. Stir frequently until sugar is dissolved and mixture begins to simmer. Remove from heat and allow to cool for 10 minutes.
• 3 In a separate large bowl, vigorously whisk together egg yolks and remaining sugar until sugar begins to dissolve (about 15-30 seconds). Sprinkle cornstarch over mixture and whisk until combined and slightly thickened.
• 4 While whisking constantly, slowly drizzle about 1/3 cup of milk mixture into the egg mixture (we’re tempering the mixture this way to keep the eggs from cooking). Gradually add remaining cream until completely combined.
• 5 Pour mixture back into saucepan and return to the stovetop over medium heat, whisking frequently until mixture begins to thicken. Remove from heat and pour through a fine mesh strainer into a heatproof bowl. Add vanilla and whisk in butter, one piece at a time, until completely melted and mixture is smooth.
• 6 Place a piece of plastic wrap directly against the surface of the pastry cream, allow to cool at room temperature for 20 minutes then transfer to refrigerator to chill completely (about 2 hours). Meanwhile, prepare cupcakes.
• 10 For the cupcakes: With an electric or stand mixer, beat together butter, oil, and sugar until light, fluffy, and well-combined (about 30 seconds on medium/high speed).
• 11 Add eggs, one at a time, stirring well after each addition, and stir in vanilla extract.
• 12 In a separate bowl whisk together flour, baking powder, and salt.
• 13 Using a spatula now rather than the electric mixer, gradually alternate adding the flour mixture and buttermilk to the butter/oil batter, starting and ending with the flour mixture and stirring until just-combined after each addition. Ingredients should be thoroughly combined, but take care not to over-mix or your cupcakes will be dense and dry.
• 14 Fill cupcake liners no more than 3/4 full (if you have extra batter discard it, don’t overfill the liners or your cupcakes will cave in), transfer to center rack of oven (I usually bake one pan at a time to ensure even baking), and bake for 17-19 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs. Allow to cool for 10 minutes in cupcake pan then transfer to wire rack to cool completely.
• 15 To assemble: Once cupcakes are cooled and pastry cream is chilled, fill a large piping bag fitted with a round tip (or use a ziploc bag with a corner cut off) with pastry cream. Use a knife to cut a 1 1/2" wide and 1" deep cavity into each cupcake (don’t cut all the way to the bottom!). Remove this core from your cupcake and then slice off the bottom so only a 1/4" thick piece of the surface remains (see pictures in post or video for a visual).
• 16 Fill cupcake with pastry cream and top with reserved 1/4" thick cupcake surface, fitting it snugly against the pastry cream. Drizzle ganache generously over the top of each cupcake, then allow ganache to harden before serving.
• 17 Store cupcakes in the refrigerator in an airtight container for up to 5 days.