Mohamed A. Moustafa Jul 22, 2010:

Dear Amel, thank you so much for the very helpful explanation. After doing some research, I am inclined to favor your suggestion regarding "house dressing" and "house seasoning" as well.
http://www.mobysonline.com/menu.htm

Arabic & More Jul 22, 2010:

I don't know if this will affect the way you decide to translate this phrase, but I thought I'd mention that a restaurant is often called a "house" in English. For example, if the restaurant owner tells you that your meal is "on the house" it means that you are not responsible for the bill...the restaurant will pay for it.

To me, "house seasoning" refers to a particular restaurant's unique blend of spices, which would be different at every restaurant.

Similarly, "house dressing" refers to a restaurant's unique recipe for salad dressing and is often a special secret that customers cannot easily duplicate at home unless they know the exact ingredients.

I am not saying the definition below is incorrect, but I wanted to add another layer of meaning to the word "house."