Successful Vegetarian Conversion

Not a lot of meat based recipes fare well under transformation to a vegetarian version.
I really don't perform this process very often, preferring to build a vegetarian recipe layer by layer to keep the integrity of the dish. However, the Portobello Tortellini soup recipe took quite well to a stripping of the meat based components and I think I actually like this version better!

Portobello Tortellini Soup (vegetarian version)
1 small sweet onion- diced
3 ribs celery-diced
3 cloves garlic- minced
3 tblsp olive oil
3 tblsp butter
1 lb Portobello mushrooms- sliced
1 pkg (12-18 oz) Three- cheese filled tortellini- fresh or frozen
2-32 oz containers of Vegetable Stock
1 tblsp Balsamic vinegar
2 -15 oz cans Diced tomatoes
¼ cup Tomato Paste
½ lb Parmesan Cheese-grated
1 tsp celery salt
1 tsp granulated garlic
2 tblsp honey
Sea salt to taste
Fresh ground pepper to taste
1 bunch fresh basil

Sauté onion, celery and garlic, in butter and olive oil over medium high heat. Add sliced mushrooms, and sauté until golden brown. Add balsamic vinegar and stir to coat well.
Add diced tomatoes with juice, and 32 oz of the vegetable stock. Simmer on low for about 30 minutes.
Boil tortellini according to package directions, do not overcook. Drain and rinse under cold water. Set aside.
To finish soup, add tomato paste, add more vegetable stock if necessary to achieve the consistency you are looking for. Add spices, and honey. Season with salt & pepper to taste.
To serve, place 6-8 tortellini in a soup bowl, ladle hot soup over pasta, sprinkle with Parmesan cheese and minced fresh basil