01 - Combine warm milk, instant yeast, and a spoonful of sugar in a small bowl. Stir gently and let rest for 5 minutes until the mixture becomes foamy and fragrant, confirming the yeast is active.
02 - In the bowl of a stand mixer fitted with a dough hook, combine the all-purpose flour, remaining sugar, and salt. Add the eggs and proofed yeast mixture. Knead on medium-low speed for 5 minutes until a shaggy dough forms. Gradually incorporate the softened butter one tablespoon at a time, continuing to knead until the dough becomes shiny, smooth, and elastic, approximately 10 minutes. Cover the bowl with a clean towel and allow the dough to rise in a warm, draft-free spot for 1 hour or until doubled in volume.
03 - Pour the whole milk into a medium saucepan and heat over medium until steaming and small bubbles form around the edges, but do not allow it to boil. In a separate bowl, whisk the egg yolks, sugar, cornstarch, and salt together until the mixture turns pale and thick. Slowly pour the hot milk into the yolk mixture in a thin stream, whisking constantly to temper the eggs. Return the combined mixture to the saucepan and cook over medium heat, whisking vigorously, until the custard thickens and coats the back of a spoon, 3 to 5 minutes. Remove from heat, stir in the vanilla extract, then transfer to a bowl. Press plastic wrap directly against the surface to prevent a skin from forming and allow it to cool completely.
04 - Preheat the oven to 350°F. Gently punch down the risen dough to release excess air. On a lightly floured surface, roll the dough into a 12-inch round. Transfer to a parchment-lined baking sheet or pizza pan. Use your fingertips to press and form a slight raised rim around the outer edge to hold the custard filling.
05 - Spread the cooled vanilla custard evenly across the dough surface, leaving a ½-inch border around the rim. Sprinkle 2 tablespoons of granulated sugar over the custard for a golden caramelized finish. Arrange fresh berries or sliced stone fruit on top if desired.
06 - Bake on the center rack for 22 to 25 minutes until the brioche edges are deeply golden and the custard is lightly set with a gentle jiggle. Remove from the oven and allow the pizza to cool for 5 to 10 minutes before slicing into 8 wedges. Dust with powdered sugar just before serving.