1. Make the Pastry Cream: The pastry cream is what gives these cupcakes their signature creamy filling, so let’s start with that. Begin by preparing the vanilla pastry cream (preferably a day in advance to allow it to chill thoroughly). In a small saucepan, whisk together the sugar, cornstarch, and flour until there are no lumps. Slowly add the cream while whisking to ensure that everything is evenly blended. Once the cream is incorporated, add the milk and continue to whisk until the mixture is smooth.

Next, crack the eggs and add the yolks one at a time, whisking thoroughly after each addition. Cut the vanilla bean in half lengthwise and scrape out the seeds with a knife. Add the seeds into the mixture along with the vanilla pod. Place the saucepan over medium-low heat and whisk continuously for 10 minutes until the mixture begins to thicken. It’s important to be patient and keep stirring to prevent the custard from curdling or scorching. Once the mixture starts to bubble, let it cook for about 5 seconds before removing it from the heat. Stir in the butter until it’s fully incorporated and smooth. If you prefer a smoother texture, you can strain the mixture through a fine-mesh sieve to remove any small curdled bits. Allow the pastry cream to cool for a few minutes, then cover it with plastic wrap, pressing the wrap directly onto the surface of the cream to prevent a skin from forming. Refrigerate for at least 4 hours until it is fully chilled.

2. Prepare the Cupcake Batter: Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners and set it aside. In a medium bowl, sift together the flour, cornstarch, baking powder, and salt. This will help ensure that the dry ingredients are well combined and that there are no lumps.

In a large mixing bowl, beat the softened butter, granulated sugar, and vanilla extract using an electric mixer on medium-high speed until the mixture is pale, light, and fluffy—about 3 minutes. Add the eggs one at a time, beating well after each addition. In a separate bowl, whisk together the milk and sunflower oil. With the mixer on low speed, gradually add the dry ingredients in three parts, alternating with the milk mixture. Start and end with the dry ingredients. Mix until everything is just combined—be careful not to overmix, or the cupcakes may turn out dense.

3. Bake the Cupcakes: Fill each muffin cup about two-thirds full with the cupcake batter. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

4. Fill the Cupcakes: Once the cupcakes are completely cooled, use a sharp paring knife to cut a small cone out of the center of each cupcake. Be careful not to cut too deep—just enough to create a small well for the pastry cream. You can snack on the little cupcake tops you cut out, or save them for later! Spoon the chilled pastry cream into the center of each cupcake, filling it up generously. Then, add another dollop of pastry cream on top of the cupcake, smoothing it out with an offset spatula.

5. Caramelize the Sugar: Once all of the cupcakes are filled with the pastry cream, place them on a baking sheet and refrigerate for about 15 minutes to allow the cream to firm up. When you’re ready to add the final touch, gently dip the tops of the cupcakes into the coarse sugar. Use a kitchen torch to carefully caramelize the sugar. Hold the torch about 2 inches above the sugar and move it in a circular motion to evenly melt and caramelize the sugar. The sugar will bubble up and turn a beautiful golden brown. Let the sugar cool and harden before serving.