In a large, heavy skillet, heat the oil over medium-high heat and saute the onion and garlic until the onions are tender and beginning to caramelize around the edges, about 5 minutes. Remove the pan from the heat and add the chicken livers and brandy. Return the pan to the heat and shake the pan to ignite. Cook until livers are lightly browned on all sides but still pink inside, 4 to 5 minutes. Add the tomatoes, crushed red pepper, bay leaf, black pepper and chicken stock to the skillet. Stir well, then let the sauce come to a simmer. Cook for 15 minutes, or until most of the liquid has evaporated. Whisk in the cream and basil. Season with salt and pepper and, if the sauce seems overly acidic, add the sugar.
Meanwhile, in a kettle or large saucepan, bring 5 quarts of water to a boil. Add the pasta and return to a boil, stirring occasionally. Cook, stirring occasionally, until the pasta is al dente, 4 to 6 minutes. Drain the pasta in a colander, then transfer to a large bowl. Remove the bay leaf from the chicken liver sauce and discard the leaf. Toss the pasta with some of the tomato sauce, then divide among serving plates. Top each serving with more sauce and some of the chicken livers. Pass the cheese at the table.