In a stand mixer with a paddle attachment, add polvilho azedo and salt. Carefully pour in the boiling water and mix on medium speed until the mixture is crumbly.
Add the oil and mix until incorporated. Then add the egg and mix until smooth.
Pour in the remaining water and mix until the dough is thick and pipeable.
Transfer the dough to a piping bag and pipe circles or sticks onto a parchment-lined baking sheet, leaving space between each one.
Preheat oven to 400°F (200°C). If you have a convection feature, use it for quicker baking. Bake for 30 minutes, or until crispy and lightly golden on the bottom. You will hear cracking sounds as they cool, which is normal.
Let the puffs cool completely before storing them in an airtight container.