Sieve the flour and salt into a bowl, then stir in the cumin seeds and peppercorns.
Add the cooled (but still liquid) ghee to the dry ingredients and mix in using your fingertips until the mixture resembles coarse breadcrumbs.
Mix in about 2-3 tbsp cold water to make a firm dough, then knead for 3-4 mins until smooth. Cover and leave for 20 mins at room temperature.
Knead the rested dough for 1 min, then divide into 15 portions (weigh for accuracy, if you like – each portion should be about 10g). Roll each portion into a ball about the size of a marble and cover with a cloth as you work to stop them drying out.
Roll each ball out on a lightly oiled surface into a 4cm disc that is roughly the thickness of a 20p coin. Prick all over using a fork to stop the mathri puffing as they cook.
Heat the oil in a wok or karahi over a medium heat, ensuring it is no more than two-thirds full, to 130°C, or until a cube of bread browns in 1 min. Working in batches, lower the mathri into the oil using a flat slotted spoon. Turn the heat to low and cook the mathri for 2-3 mins on each side until pale golden. Drain on kitchen paper and leave to cool. Will keep in an airtight container for up to two weeks. Top the mathri with Indian pickle and serve at room temperature with masala chai.