Heat a deep soup pot over medium heat. Add 2 Tbsp. olive oil and swirl it around to evenly distribute it.
Add 2 finely chopped celery stalks and 2 Tbsp. garlic (minced or paste) and saute for about 3 minutes.
Add 2 lbs. chopped shrimp.
Add 2 finely chopped green onions and saute both for about 2 to 3 minutes.
Melt 1/2 stick butter in the pot and cook for an additional 1-2 minutes.
Spread 3 Tbsp. flour over the ingredients in the pot. Cook for 5 minutes, constantly stirring.
Pour in 1 cup white wine while continuously stirring. Let it simmer and thicken. When it is thick enough, it will take longer to pool back to the center of the pot when pushed with a spatula (see photo below).
Add 2 cups of tomato sauce and let it bubble and thicken while continuing to stir.
Once it thickens, add 64 oz. chicken broth and let it simmer. Turn the heat to low and wait for it to cool off somewhat.
Add in 2 cups half & half SLOWLY while stirring for about 1 minute!
Sprinkle in 1/2 cup of Parmesan SLOWLY while continuing to stir for about 2 minutes!
Turn heat back to medium and let the soup sit until it starts to bubble. Season with salt & pepper to taste, and serve!