Courtesy of Chef Faizal Kassam of Cibo Trattoria.
Preheat grill to 450ºF.
For the polenta: In a heavy saucepan, bring the milk and stock up to a boil.
Whisk in the polenta in a thin stream. Cook on medium heat for 2.5-3 hours, stirring occasionally.
Season and keep in a bain marie (water bath). Before serving, heat up the polenta, adding more milk if needed to thin it out. Whisk in Parmesan and butter to finish.
For the onions: In a saucepan over medium high heat, cook the cipollini onion until it changes into a translucent colour. Add the balsamic vinegar and reduce until sticky. Add 1 tsp of butter. Set aside.
For the liver: Heat a large pan over medium high heat. Season the liver with kosher salt and black pepper. Grill both sides until medium rare (1-1.5 min per side). Rest for 4 minutes, then slice into 2 pieces.
To serve: Spoon the polenta onto the plate, and add the liver pieces and onions. Drizzle with aged balsamic and olive oil. Garnish with sage leaves.