Kasha Stuffed Tomatoes

• 6 firm
• 2 garlic (cloves)
• 1 celery rib
• 1 kasha (uncooked)
• 1/2 scallions
• 1/2 shell
• 1/2 from tomato
• 475 ml vegetable broth (hot)
• 85 gr mushrooms
• 60 ml water