I love these (called Sabudana Vada) – here’s a version that’s pan-fried (though deep fried are lovely when fresh!)
Is minute tapioca ground up or just pre-cooked? if the latter, you could probably use it without soaking, just proceed to mix with potato and seasonings.
Any green chutney works, or green zhoug, as a dipping sauce, though I gobble them them plain most of the time 
(You may also enjoy sabudana khichdi, which he doesn’t give a recipe for because it’s trickier, but is a loose / sauteed version of the same ingredients and flavors – like this.)
