Peel and cut the potatoes in half, and then quarters. Transfer to a pot with water and boil till cooked.
Defrost the peas.
Meanwhile, finely chop the ginger, chillies and coriander (both leaves and stems)
Once the potatoes have cooked, drain the water and mash.
Heat oil in a pan over medium heat and add the cumin seeds and asafoetida. Allow them to bloom (cook in the oil) for 30 seconds.
Add the ginger and chillies and fry for a minute or two.
Add the turmeric (reserve a pinch for the plant-based milk wash) and mix.
Now add the mashed potatoes and mix.
Add the peas and kala namak and mix to combine. Cook for 5 minutes, stirring continuously to ensure nothing gets stuck to the pot.
Add the Amchur powder and chopped coriander. Mix to combine.
Take off the heat and transfer it onto a large plate or tray to cool.
Remove the shortcrust pastry from the fridge to allow it to come up to room temperature.
Gently unroll the pastry on the countertop, leaving the butter paper in (it will come in handy when transferring the log into the fridge). Spoon the cooled potato mix onto the pastry and spread it evenly, leaving ½ a cm on the sides and 1 cm on the top end (see photographs)
Mix turmeric with the plant-based milk and brush the edges of the pastry.
Gently start rolling from the bottom end towards the other end. Attempt to roll as tight as possible. Once you reach the top end, brush with the plant-based milk/turmeric wash and seal the end. Press pastry to ensure a tight seal.
Brush the log with the plant-based milk/turmeric wash and transfer to the fridge for about 10 to 15 minutes. When the pastry is firm it is easier to cut it into the pinwheel portions.
Once chilled, cut the log into one-inch width portions with a sharp knife. Cut using a sawing motion. Pressing down the knife will ruin the shape of the pinwheels. You will have about nine pinwheels.
Transfer the pinwheels onto a tray lined with parchment paper and return back to the fridge.
Preheat oven to 190ºC. (fan assisted)
Remove the pinwheels from the fridge and transfer them into the oven. They have cooked when the pastry is golden. Bake for 25 to 30 minutes, turning the tray midway. They have cooked when the pastry is golden.
Once baked, leave on the counter to cool for five minutes. Serve with a side of coriander and mint chutney or ketchup.