Heat a tablespoon of olive oil in a medium pot over medium heat. Add the onion, garlic, and mint, and sauté until the onion becomes soft and translucent.

Add the cubed potatoes and chopped tomatoes to the pot. Allow them to cook together, stirring occasionally, for about 3 to 4 minutes to combine the flavors.

Incorporate the mixed fish into the pot, then add 6 cups of water and season with salt. Bring the mixture to a boil.

Once it's boiling, reduce the heat to a simmer, cover the pot, and let it cook gently for about 30 minutes for the flavors to harmonize.

Check the seasoning and adjust the salt if necessary. To serve, place 2 or 3 slices of Italian bread at the bottom of each bowl, ladle the hot soup over the bread, and drizzle with a bit of olive oil before enjoying.