In a large pot, sauté the onion in a generous pour of olive oil over gentle heat, until it becomes soft and translucent. Add the garlic and let that, too, sauté until it just begins to give off its fragrance. (Add the anchovy at this point, too, if using, and let it 'melt'.)
Now add the shredded Swiss chard and give it a good turn so it is completely coated with the soffritto. Season with salt and pepper. Let the chard simmer for a few minutes, until it has wilted.
Add the chickpeas, drained of their liquid. (If using canned, rinse them as well.) Give them a turn and then add the tomatoes. Turn up the heat a bit to bring everything to a simmer. Simmer for 30 minutes, topping up with water (or the chickpea cooking liquid if you've boiled them yourself) as needed.
Serve while still warm, with a drizzle of best quality olive, along with a good grinding of black pepper and freshly grated pecorino if you like, along with toasted slices of crusty bread, preferably homemade.