Preheat your oven to 350°F (175°C) and line a 12-cup muffin pan with cupcake liners.

Combine granulated sugar, cornstarch, and all-purpose flour in a saucepan, then whisk in whole milk and heavy cream. Heat until thickened, then stir in vanilla seeds and cool.

Sift together flour, cornstarch, baking powder, and salt. Beat butter, sugar, and vanilla until fluffy. Add eggs one at a time, then alternate flour mixture and milk/oil until combined.

Fill muffin cups two-thirds full and bake for 18-20 minutes. Cool in the pan for 5 minutes before transferring to a wire rack.

Cut a cone from the center of each cooled cupcake, fill with pastry cream, and spread more cream on top. Chill briefly.

Sprinkle coarse sugar over the cream and caramelize with a kitchen torch until golden.