Step 1: Prepare the Pastry Cream

1. Follow the Easy One Pot Vanilla Pastry Cream recipe.
2. Allow the pastry cream to chill in the refrigerator for at least 4 hours or overnight to ensure it thickens properly.

Step 2: Make the Cupcake Batter

1. Preheat the Oven: Preheat the oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.
2. Cream Butter and Sugar: In a large mixing bowl, beat the softened butter, granulated sugar, and vanilla extract with an electric mixer for 3 minutes until light and fluffy.
3. Add Eggs: Add the eggs one at a time, mixing well after each addition until the mixture is smooth.
4. Mix Dry Ingredients: In a separate bowl, whisk together the flour, cornstarch, baking powder, and salt.
5. Combine Wet Ingredients: In a small bowl, whisk together the milk and oil until well blended.
6. Finish the Batter: Add one-third of the dry ingredients to the butter mixture, mix, and then add half of the milk mixture. Repeat, alternating between the dry and wet ingredients, ending with the dry. Mix until smooth, but don’t overbeat.
7. Bake: Spoon the batter into the cupcake liners, filling each two-thirds full. Bake for 18–20 minutes or until a toothpick inserted comes out clean. Cool the cupcakes on a wire rack.

Step 3: Fill the Cupcakes

1. Use a small paring knife to cut a cone-shaped hole in the center of each cupcake.
2. Spoon the chilled pastry cream into each hole and smooth the top with a small offset spatula.

Step 4: Caramelize the Sugar

1. Sprinkle coarse sugar evenly on top of each cupcake.
2. Use a kitchen torch to melt and caramelize the sugar until golden brown and crackly. Allow the sugar to set for a few minutes.