The Preparation
Combine 1 cup whole milk, 1/2 cup vegetable oil, and salt in a pot. Heat on medium, stirring with a wooden spoon, until large bubbles form and it comes to a boil.
Remove from heat. Add the tapioca flour all at once and stir vigorously — the mixture will look like wallpaper paste or paper mache. This is normal.
Transfer the dough to a stand mixer fitted with the paddle attachment. Mix on medium speed for about 2 minutes to cool the dough and smooth it out.
Add eggs one at a time, mixing until each is fully incorporated before adding the next. The dough will become silky, stretchy, and smooth.
Scrape down the sides of the bowl. Add 1 1/2 cups grated Parmesan cheese and mix until evenly distributed.
Preheat oven to 350°F. Set two racks evenly spaced in the oven.
Using a #40 ice cream scoop (about 1.6 tablespoons) dipped in water, scoop dough onto two parchment-lined baking sheets, spacing about 1 inch apart. Makes about 24 puffs.
Bake for 15 minutes, then swap the top and bottom trays and rotate them. Bake another 15-20 minutes until golden brown.
Optional: sprinkle with flaky salt when they come out of the oven.
