To begin, preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat to prevent the crackers from sticking. These crackers puff up quickly, so ensure the sheet is ready before starting.

In a medium saucepan, combine the water, vegetable oil, and salt. Bring the mixture to a gentle boil over medium heat. This step is key to ensuring the starch hydrates properly. Once the mixture is boiling, remove it from the heat.

In a large mixing bowl, place the tapioca starch. Gradually pour the hot water and oil mixture over the starch, stirring constantly with a wooden spoon or spatula. This will scald the starch, giving the dough its unique texture. Stir well until you get a smooth mixture.

Let the mixture cool for about 5 minutes. Once it’s cool enough to handle, add the egg. Stir the dough well until the egg is fully incorporated. The dough should be sticky but smooth. If it feels too thick, add a tablespoon of water at a time until it reaches a pipeable consistency.

For a perfectly crunchy texture, you can add optional seasonings like black pepper or chili flakes at this point. Taste the dough for salt and adjust if necessary. Biscoito de polvilho traditionally has a mild flavour, but a little spice can elevate it.

Transfer the dough to a piping bag or a plastic bag with a small tip cut off. Pipe the dough onto the prepared baking sheet in long, thin strips or circular shapes, leaving some space between each piece. The dough will puff slightly during baking, so aim for uniform sizes to ensure even cooking.

Place the baking sheet in the preheated oven and bake for 20-25 minutes, or until the crackers are puffed and slightly golden. The exact time may vary depending on your oven and the size of your crackers. They should feel firm and crispy when done but still light and airy.

Once baked, remove the crackers from the oven and allow them to cool on a wire rack. Biscoito de polvilho is best enjoyed fresh, as its texture is at its crunchiest. Serve alongside coffee or tea, or enjoy as a savoury snack throughout the day.