01 - Combine warm milk, instant yeast, and a small spoonful of sugar in a bowl. Let the mixture rest for 5 minutes until it becomes foamy and active.
02 - In a stand mixer fitted with a dough hook, combine the flour, remaining sugar, salt, eggs, and proofed yeast mixture. Knead on medium speed for 5 minutes. Gradually incorporate the softened butter, one piece at a time, and continue kneading until the dough is smooth, shiny, and elastic, about 10 minutes.
03 - Cover the dough with a clean kitchen towel or plastic wrap and let it rise in a warm, draft-free spot for 1 hour, or until doubled in bulk.
04 - Heat the milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together the egg yolks, sugar, cornstarch, and salt until the mixture turns pale and smooth. Slowly stream in the hot milk while whisking constantly to temper the yolks.
05 - Return the mixture to the saucepan and cook over medium heat, whisking continuously, until it thickens considerably, 3 to 5 minutes. Remove from the heat, stir in the vanilla extract, then press plastic wrap directly against the surface and let cool completely.
06 - Preheat the oven to 350°F. Punch down the risen dough and roll it out on a lightly floured surface into a 12-inch round. Transfer to a parchment-lined baking sheet or pizza pan. Use your fingers to press a slight raised rim around the edge.
07 - Spread the cooled custard evenly over the dough, leaving a 1/2-inch border around the rim. Sprinkle with 2 tablespoons of granulated sugar to promote caramelization. Arrange fresh fruit on top if desired.
08 - Bake for 22 to 25 minutes, until the crust is deeply golden and the custard is lightly set. Allow to cool slightly before slicing into 8 wedges. Dust with powdered sugar just before serving.