Stir in the tomato sauce, chicken broth, brown sugar (if using), vinegar (if using), and bay leaf. Bring to a simmer, then lower the heat to medium-low. Simmer for 10 minutes, stirring occasionally, until the sauce thickens enough to coat a spoon. Taste and adjust heat, salt, or acidity. If it tastes flat, a tiny splash more vinegar helps. If it tastes too intense, add a splash of broth or water.