Prep the Vegetables: Cut the broccoli and cauliflower into bite-sized pieces. Chop the onion, carrots, and celery.
Saute Aromatics: In a large pot, melt the butter over medium heat. Add the chopped onion, carrots, and celery. Saute until softened, about 5-7 minutes.
Add Flour: Sprinkle the flour over the sauteed vegetables and stir to combine. Cook for about one minute, allowing the flour to cook slightly.
Add Vegetable Stock: Gradually pour in the chicken stock, stirring constantly to avoid lumps. Add the broccoli and cauliflower to the pot.
Simmer: Bring the soup to a boil, then reduce the heat to low. Cover the pot and let the soup simmer for about 25 minutes, or until the vegetables are tender.
Optional Blending: If desired, use an immersion blender to blend the soup until smooth. This step is optional and depends on your preference for soup texture.
Add Cream and Cheese: Remove the soup from the heat and stir in the heavy whipping cream and shredded cheddar cheese until the cheese is melted and the soup is creamy.
Season: Add Vegeta seasoning, if using, and season the soup with salt and black pepper to taste.
Serve: Ladle the hot soup into bowls and garnish with additional shredded cheese or fresh herbs if desired. Serve hot and enjoy the comforting flavors of this Cheese Broccoli Cauliflower Vegetarian Soup!