First, make the malasada dough. In the bowl of a stand mixer fitted with a dough hook, combine the flour, sugar, yeast, and salt. Knead on low to combine, about 30 seconds. Press a tall glass or measuring cup in the center of the ingredients to make a "well."
Whisk the wet ingredients. In a large liquid measuring cup, whisk together the milk, egg, egg yolk, and butter.
Knead the dough. Pour the wet ingredients into the well in the dry ingredients and knead on medium-low for 10 minutes, or until smooth and elastic, using a rubber spatula to scrape down the bottom and sides of the bowl as necessary. The dough will be sticky and thick. It will look more like batter at this point, but that's totally okay, I promise! Proof the dough overnight. Cover with plastic wrap and refrigerate overnight.
While the dough is proofing, make the passion fruit pastry cream. In a medium, heavy-bottomed saucepan, whisk together ¼ cup (1.75 ounces or 50 grams) of the granulated sugar and the milk. Cook over medium-low heat, whisking continuously, 2 to 3 minutes or until the milk begins to steam. Reduce the heat to low.
Whisk together the egg, cornstarch, and remaining sugar, then temper it with the hot milk mixture. In a medium, heatproof bowl, whisk together the egg, cornstarch, and remaining sugar.Slowly ladle ¼ cup of the hot milk mixture into this egg mixture, whisking the egg mixture continuously. Pour the egg mixture into the saucepan with the remaining hot milk mixture and bring to a boil over medium heat, whisking continuously. Immediately remove from heat. Add the butter, passion fruit, and vanilla. Immediately add the butter, passion fruit, and vanilla and whisk until smooth.
Chill the pastry cream overnight. Place a fine-mesh sieve over an airtight container with a lid and pour the pastry cream through the sieve to remove any lumps. Set the bowl on a wire rack. Press a sheet of plastic wrap directly against the surface of the pastry cream and cool completely. Cover with the lid and refrigerate overnight.