I live in New Jersey, but sometimes travel to New York City for work. The street carts there make this lamb platter with rice and salad. They put this heavenly white sauce on it. Tastes a little like mayo, but I have no clue what else is inside. Some carts may make it a bit differently, but most of the ones I've tried are similar. No matter what cart I visit, I can pretty much guarantee it'll be fantastic to my taste buds. Some of the carts also make a spicy cilantro sauce. At least they told me it was made with cilantro. Each time I try and ask about the white sauce I get a different answer it seems.
The only problem with my white sauce craving is getting to the city. It's about a 7 minute drive to the train station, but I have to pay for parking and almost $30 for a train ticket! Actually, make that double because my Girlfriend probably wants to go also. I set out searching the internet for this recipe, but no one seems to have one. I did, however find a recipe that was a little similar, and I enjoyed it enough to make twice already. It'll never replace the white sauce from the city, but it's not bad:
1/2 cup Mayonnaise
1/4 cup Water
1/4 tsp Horseradish
1/4 tsp Salt
1/4 tsp Pepper, Black
1 tsp Sugar
1 tsp Lemon Juice
2 tbsp Malt Vinegar
Mix it all in a blender. Enjoy. You don't have to add the sugar, but then it becomes even more tangy from the vinegar. I should note that I've made this twice before. The first time I put in the vinegar using an actual tablespoon. The second time I used a measuring tablespoon. That measuring spoon seems larger than a tablespoon? The second time was too much vinegar flavor, so I added some more mayo. Still came out alright.
By the way, if anyone knows a food science lab that can examine food and give me a recipe, I'd pay for it. I'd also be interested in finding out a certain chili sauce recipe.