In a large saucepan over medium heat, add butter. When it starts sizzling, add onions and sauté until barely soft, about 2 minutes. Add celery and cook for 2 minutes.
Add peppers and sauté until almost tender, about 2 minutes.
Add mushrooms and sprinkle with salt and pepper, stir well. Cover and sauté for 3-4 minutes or until it reduces by half.
Remove the saucepan from the heat and transfer the vegetables into a Dutch oven; set aside.
Preheat oven to 375ºF.
Return the saucepan to the heat and add ground beef; cook until no longer pink. Just before it’s done, add pressed garlic; sauté for 1 minute.
Remove from the heat and transfer to a colander to drain any excess fat.
Transfer the drained meat to the vegetables before adding tomato soup, crushed tomatoes, tomato juice, and seasonings; mix well.
Cover the top with cheese slices and sprinkle with parsley.
Transfer to the preheated oven and cook for 30 minutes or until heated through.
Turn to broil and cook until the cheese is golden, about 3 to 5 minutes.
Notes
Footnote: If you prefer using fresh herbs, the ratio is 3:1 so you'll need 1 tbsp. of each.