In a pot, heat the olive oil. Add the garlic, scallions, leeks and shallot and cook over moderate heat, stirring occasionally, until the leeks are softened, 6 minutes. Add the anchovy, crushed red pepper, spaghetti, stock, cream and the 1/2 teaspoon of salt and bring to a boil. Reduce the heat to low and cook, stirring, until the pasta is tender and a sauce forms, 11 minutes. Stir in the chives and 1/4 cup of cheese; season with salt. Serve the pasta with extra cheese on the side.