Im not sure what "restaurant level" means. But, corn soup is only as good as the corn that you use to make it.
Here's a quick and dirty recipe.
4 Tbsp butter;
6 ears fresh picked corn;
6 to 8 cups quality chicken broth or stock;
1 cup shallots, minced
1/2 white or yellow onion, minced
Kosher salt
Fresh ground black pepper
Fresh picked herbs of your choice to garnish
With a sharp knife, remove the kernels from 5 of the 6 ears of corn making sure only to cut the crowns leaving the hulls on the cob. Reserve one whole cob. Turn the knife over and using the top of the blade, scrape the cob to remove the remaining kernels and the corn "milk." Break the cobs into thirds and reserve.
In a large pot, melt the butter. Add the shallots and onion with a healthy pinch of kosher salt. Saute until the onions are soft and translucent; about 8 to 10 minutes. Add the broth, kernels, broken cobs and whole ear of corn to the pot. Bring to a generous boil and reduce heat to a gentle simmer. Cook for 10 minutes. Remove the whole ear of corn and set aside. Let simmer for another 10 minutes, remove the broken cobs and discard.
With an immersion blender or food processor, puree the soup until very smooth. Strain the soup through a fine sieve into a large bowl, pushing the liquid through with a ladle or rubber spatula until nothing but the fibrous bits are left behind. Discard what's left in the sieve.
Return the soup to the stove over low to medium heat. The soup should be creamy. If too thick, add more broth. If too thin, let reduce until it reaches the desired consistency. Remove the kernels from the last ear of corn in the same way as before. Add the kernels and the corn "milk" to the soup. Gently simmer for 5 to 7 minutes or until the kernels are just soft. Taste for seasoning and adjust accordingly.
Ladle into warm bowls and garnish with fresh picked herbs.
For a more spicy end product, add a diced jalapeno or similar pepper with the kernels from the last ear of corn, seeds and ribs removed or add a pinch of Cayenne or white pepper. I prefer the peppers.
For a "smoky" twist, dice 2-3 strips of thick cut smoked bacon, fry separately and add with the kernels from the last ear of corn.
Enjoy,