Soak the saffron stigmas in two tablespoons of hot water for at least 20 minutes, mashing them with a teaspoon.
Beat the eggs with the sugar, the oil, the salt and two tablespoons of water in which the saffron stigmas were found. Then add the sifted flour with the baking powder and the chocolate chips. Make a ball, wrap it in plastic wrap and let it rest in the fridge for 30 minutes.
Then form two uniform rectangles approximately one centimeter high. Place them well away from each other (they will rise a lot) on a baking sheet lined with parchment paper and sprinkle the surface with demerara sugar.
Bake at 170 ° C for 20 minutes. Remove the rectangles from the oven, cut them into slices and then put them back on the oven tray with the cut side facing up.
Bake the biscuits again for another 5 minutes.
Leave to cool on a wire rack. Store in an airtight container where they can be kept for several days.