Preheat the oven to 400º and line a baking sheet with parchment paper. In a medium saucepan, combine the milk, salt and butter, and bring to a boil. Remove from the heat and whisk in the tapioca flour until incorporated.
Transfer the mixture to a stand mixer fitted with the paddle attachment. With the motor running on low speed, add the eggs, one at a time, until incorporated, followed by 1½ cups of the grated Parmesan.
Scoop 2-tablespoon-size balls of dough onto the prepared baking sheet, spaced 1 inch apart. Sprinkle the remaining Parmesan over the balls of dough.
Bake until golden brown and puffed, 20 to 25 minutes. Remove from the oven and transfer to a platter. Serve warm.