Wash and pat the fish pieces dry. Sprinkle with salt and pepper and set aside.
In a medium pot with a lid bring 4 cups of water to a boil.
While the water is to coming to a boil, prepare the hash.
Cut the dark ends of the leeks off and the root (you only want the white and light green parts). Cut the leeks into 1/4" rings. Rinse very well under running cool water. I use a wire mesh strainer to do this. Leeks are very sandy and need to be cleaned well.
In a medium sized skillet over medium-high heat, add 1 Tablespoon oil. Cook the pancetta for about 3-4 minutes and then add in the leeks and diced sweet potato. Cook an additional 5-7 minutes or until the pancetta is crispy and the potato and leeks are tender. Season with salt and pepper and add in the sage.
Once the water comes to a boil add the cornmeal whisking as you pour in the cornmeal. Add 1 1/2 teaspoons Kosher salt, 1/2 teaspoon black pepper and 1 teaspoon granulated garlic. Lower the heat to low and cover. Let cook about 15 minutes or until the polenta is creamy and cooked through. Once it is cooked through stir in grated Parmesan cheese and 1 Tablespoon butter. If the polenta becomes too thick just add a little bit of water to thin it out. You want it thick, but not gluey.
In a large non-stick skillet add 2 Tablespoons oil to pan over medium-high heat. Once the pan is hot add the fish and move it ever so slightly so it does not stick. Cook about 4-5 minutes per side or until the fish flakes easily with a fork and is opaque all the way through.
Divide the polenta between 4 plates. Place a piece of fish on top of polenta. Spoon hash over fish and polenta.