In a medium pan of salted, boiling water, cook the potatoes for 12 mins, or until tender.
While the potatoes are cooking, make the salsa: In a bowl, combine the extra-virgin olive oil, vinegar, lime zest, and half the lime juice, the chilli, half the garlic, and the coriander. Season and add extra lime juice to taste, if you like.
Heat 1 tbsp olive oil in a large frying pan over high heat. Season the flour and use to coat the basa fillets, then add them to the pan. Fry for 30 secs over high heat, then reduce the heat to medium-high and fry for a further 2 mins each side, or until golden and cooked through.
Drain the potatoes. Return to the pan, along with the remaining olive oil and garlic. Lightly crush with a potato masher or a fork, then divide between 2 plates. Top with the fish and drizzle over the chilli and coriander salsa.