Put the dried chickpeas in a bowl and cover them with cold water by about 5 cm / 2 inches. Soak for 8 hours or overnight, until they've roughly doubled in size, then drain well.
Pulse the drained chickpeas in a food processor in 10 to 12 short bursts, scraping down the sides once, until they look like coarse couscous. Don't add water, and stop before they turn into a paste.
Tip the chickpeas into a large bowl with the tomatoes, onion, mint, parsley, flour, baking powder, cumin, salt and pepper. Mix with a spoon until the batter holds together when you squeeze a little in your hand. Let it rest for 15 minutes so the flour can soak up some of the moisture.
Pour the olive oil into a 26 cm / 10-inch heavy skillet and heat over medium heat to 175 C / 350 F, about 4 minutes. Drop in a small pinch of batter. It should sizzle steadily right away.
Scoop 2 tablespoons of batter, press it into a flat round about 6 cm / 2 1/2 inches wide and 1.5 cm / 3/4 inch thick, and slide it into the oil. Fry a test batch of 2 to 3 fritters for 3 minutes per side, until deep golden and crisp. If one falls apart, stir 1 more tablespoon of flour into the batter, and taste a fritter to check the salt.
Fry the rest in batches of 5 to 6, about 3 minutes per side, so the pan never gets crowded. Lower the heat a little if the fritters brown in under 2 minutes. Move each batch to a wire rack, which makes about 20 fritters in total.
Serve warm within 20 minutes of frying, with lemon wedges and a pinch of flaky salt if you like.