Sift the flour onto a wooden board (you may use the stand mixer, or KitchenAid, fitted with a dough hook); then sift in the salt and baking soda;
Add room-temperature lard or oil. Smash the lard with the tips of your fingers and combine it with the flour until it is completely incorporated;
Mix with a fork while taking a little flour from the sides each time; then add the water in gradually. Start mixing with your hands until the dough comes together. Add more flour if the dough is sticky;
Knead the dough vigorously until it’s smooth and elastic;
Divide the dough into 8-10 even balls; they should be as big as a tangerine;
Place the balls to rest for at least 2 hours (you may use the dough without letting it rest, but it will be less tasty);
After the resting period, flour the pastry board, and on a smooth surface (a marble surface is perfect), roll the ball into a disc roughly 8-10 inches (20-25cm) in diameter and very thin (2mm). Try to make them as round as possible: always keep the rolling pin in the same position while you are rolling the ball. Rotate the dough at a right angle instead.
If the piadina sticks to the rolling pin, sprinkle the surface with a little flour;
Heat a griddle or a non-stick pan; cook the piadina over medium heat;
Gently prick the surface to avoid bubbles;
It takes a few minutes; cook the piadina a couple of minutes on each side or until it’s golden; use a spatula to flip it over. The piadina is done when it shows leopard-like spots.
Add your favorite fillings. Below are a few suggestions.