Cook Polenta: Bring water to a boil. Gradually whisk in polenta. Cook for 35-40 minutes, stirring occasionally. Season with salt midway. Once cooked, stir in Parmesan and a knob of butter.
1 ⅔ cups polenta, ½ cup grated Parmesan cheese, Salt to taste, 2 tablespoons butter
Cool Polenta: Spread the cooked polenta in a high-sided tray, no more than 1 inch thick. Let it cool completely.
Prepare Liver Mix: Chop the onion and lightly brown it in a skillet with oil, sage, and desalted anchovies. Add chicken livers and cook on high heat for 4 minutes.
½ onion, 3 anchovy fillets, 4 sage leaves, 1 ⅔ cups chicken livers
Add Wine: Deglaze with Vin Santo, cover, and simmer on low heat for 20 minutes. Add water if too dry.
⅓ cup Vin Santo wine, 1 ¾ cups water
Blend Liver: Once cooked, blend livers with a knob of butter, a drizzle of oil, and a pinch of salt and pepper. Let it rest.
Pepper to taste
Bake Polenta: Cut the cold polenta into rectangles and bake at 390°F for 5 minutes or until crispy. Optionally, you can also fry them in oil. Once the oil reaches about 180°C (356°F), submerge the polenta slices and fry them for about ten minutes, until they turn golden brown.
Spread and Serve: Spread liver sauce on the polenta crostini and serve hot.