White sauce commonly referred to as "halal white sauce" typically is a creamy, tangy sauce made with ingredients like mayonnaise, Greek yogurt or sour cream, white vinegar, lemon juice, garlic, parsley, salt, and black pepper. This sauce is popular on halal food carts, especially New York City halal carts known for chicken and rice dishes. Regarding its halal status:

• The ingredients used (mayonnaise, yogurt, vinegar, lemon juice, garlic, herbs, and spices) are halal by nature since they do not contain any pork, alcohol, or non-halal meat products.
• The sauce is known as "halal white sauce" because it is a staple condiment used in halal food carts that serve halal meat dishes compliant with Islamic dietary laws.
• The recipe is purely vegetarian (dairy-based) and does not typically include any non-halal substances.

Therefore, white sauce as served in halal carts and made with these typical ingredients is halal. It is designed to accompany halal meals and is free from any haram (forbidden) components. In summary, white sauce labeled as halal white sauce is halal and safe for those following halal dietary restrictions. The key is ensuring it is prepared following halal hygiene and ingredient standards, which is usually the case at halal food vendors.