Sago is known as javvarisi in tamil.
This variety used for vadai & upma is called “ disco javvarisi” or small nylon variety.
To give an idea how it looks like, I am attaching a photo below.
Small nylon javvarisi - 1 cup
Potatoes - 2 big or 3 medium
Coarsely powdered, roasted groundnuts - ½ cup
Red chillii powder - 2 tsp
Oil - to deep fry
Salt
Finely chopped coriander leaves - 2 tbsp
Soak javvarisi ( sago) in 1 cup + 1 tbsp water for 5-6 hrs.
The quantity of water is important.
More water will make it sticky when cooking.
When it is soaked well, strain just to make sure, any excess water drains off.
Boil, peel & mash the potatoes well.
Mix the drained sago with powdered groundnuts, mashed potatoes, salt, red chilli powder & chopped coriander leaves well to form a dough.
Do not add water.
Pat vadas with hand ( discs 2” size).
You can refrigerate them in a box lined with butter paper & keep them ready.
Just before serving, deep fry in hot oil on medium flame till bubbles subside.
Serve hot with tomato sauce.