From my words: http://dangermencooking.blogspot.com/2009/08/enchiladas-suizas.html Addendum. On 31 October 2013, I see that this recipe became a topic of discussion at the eGullet forum. The original poster asked about the sauce used at Sanborn's in Mexico City. I immediately want to point out that Mexican Cuisine is far more regional and local than United States Cuisine and as such the sauce which was queried about may be local to Sanborn's in Mexico City and not any other Sanborn's in Mexico. As the original poster asked about a salsa verde, without tomatillos, I may have a solution. Only her father's taste buds would know for certain. The first secret ingredient is solved by the inclusion of information I have previously not put online. Please forgive. Crema de Rancho Cream separating from the milking, left overnight to rise to the top and skimmed off is set aside to ferment. The longer the fermentation the higher the percentage of lactic acid development. Salt is then added and if the crema is not sour enough, it is again set aside to allow the lactic acid to increase. According to my research, it should not get as sharp (piquant) as crema agria or in English, sour cream. Crema de Rancho is sold under the following names: Crema de Rancho crema espasa [thick cream] crema de la buena crema especial crema de primera crema de al mejor The second secret ingredient is likely to be hoja santa and I won't show all the variant spellings for this herb or ingredient. The plant, widely used in Mexico, is botanically named: Piper Auritum. I have posted about this plant at Danger! Men Cooking! as I have only recently been able to obtain it commercially. While I have not eaten Enchiladas Suizas in Mexico City, at the Sanborn's the original poster at eGullet queried about, I am pretty sure this may be what she is after, although good luck finding some fresh from the cow warm milk to ferment. Looking at the Sanborn's menu, I see that the few listed ingredients do have crema and salsa verde, so my best guess for the lady looking to reproduce their recipe is to cook the hoja santa and blend it to a puree, whence, add the sour cream and use it as Sanborn's salsa verde. I'm uncertain as to whether the enchiladas suizas have a garnish of Swiss Cheese, I guess they are using a Mexican cheese.