Add minced garlic, minced ginger, chilli powder, turmeric powder, and salt to a large bowl and mix to a thick paste. Fingers are best for this job. Tip in the anchovies and toss to coat all the pieces evenly. Leave to marinate for at least two hours (or overnight for best results). If you are short on time, it can be used right away.
Heat coconut oil over medium heat. Mix semolina and corn flour together on a plate and set aside.
Take a few pieces of the fish and dredge them in the semolina-corn flour mixture before dropping them into the oil. Make sure not to overcrowd the pan. Fry the anchovies for 1-2 minutes until golden and transfer to a paper towel. Repeat in batches.
Once the anchovies are all fried, drop the sprigs of curry leaves into the oil until they crisp up. Make sure to stand back for this step as the curry leaves will pop and sputter. Drain on paper towels.
To serve, I like to scrunch up some of the crispy curry leaves in my hand and use as a garnish for the anchovies. Serve with lemon wedges.