In the bowl of a stand mixer fitted with a dough hook, combine flour, sugar, yeast, and salt. Knead on low to combine for about 30 seconds. Press a tall glass in the center of the ingredients to make a 'well'.

In a large liquid measuring cup, whisk together the milk, egg, egg yolk, and butter.

Pour the wet ingredients into the well in the dry ingredients and knead on medium-low for 10 minutes until the dough is smooth and elastic. The dough may be sticky and thick.

Cover the dough with plastic wrap and refrigerate overnight.

In a medium saucepan, whisk together ¼ cup of sugar and whole milk. Cook over medium-low heat, whisking continuously for 2 to 3 minutes until steaming. Reduce the heat to low.

Whisk together the egg, cornstarch, and remaining sugar, then temper it with the hot milk mixture. Slowly ladle ¼ cup of the hot milk mixture into the egg mixture while whisking continuously.

Pour the egg mixture back into the saucepan with the remaining hot milk mixture and bring to a boil over medium heat, whisking continuously. Remove from heat.

Add the butter, passion fruit puree, and vanilla, whisking until smooth.

Pour the pastry cream through a fine-mesh sieve into an airtight container to remove lumps. Cover with plastic wrap and cool completely. Refrigerate overnight.

Line a half sheet pan with parchment paper and generously flour the paper.

Remove the dough from the refrigerator, uncover, and discard the plastic wrap. Tip the dough onto a floured counter and roll into a rectangle about ½-inch thick.

Use a 3-inch round cookie cutter to cut out 6 circles. Gather and reroll any remaining dough as needed.

Place the circles on the prepared sheet pan, cover loosely with plastic wrap, and let rise for 1 hour.

Fill a pot with vegetable oil and heat to 365°F, using a deep-fry thermometer.

Line a wire rack with paper towels. Place the ¾ cup of granulated sugar in a shallow bowl for tossing.

Carefully remove the donuts from the pan and fry 2 donuts at a time for 2 minutes on each side until puffy and golden brown.

Move the fried donuts to the prepared wire rack and repeat until all are fried, maintaining the oil temperature.

Toss each donut in the bowl of sugar while still warm.

After 15 minutes, use a skewer or Bismark pastry tip to poke a hole in the side of each donut and pipe the pastry cream into the holes until plump.

Serve warm or at room temperature. Store any leftovers under a cake dome or a large bowl for up to 1 day. Refrigerate for up to 2 more days after that.