Par boil rice in chicken broth for 5 minutes or until slightly softened.
Drain and set aside BOTH rice AND broth.
Brown garlic, pepper, celery and onion over medium heat.
Mix in rice and rosemary, and ladle broth over top until rice is covered. Lower to medium-low heat. Cover and cook for 10-15 minutes.
While rice is cooking, cube the tuna steak (about 1/2 inch cubes), season with black pepper and pan sear on high heat for 30 seconds on each side. Lay on top of rice and let cook at least five minutes.
Heat broiler to 350°F.
When rice is soft and broth fully reduced, mix in cream. Let cook two minutes and then set aside to steam for five minutes.
Cut thin slices of mozzarella.
Dish risotto into oven safe plates (ceramic pie plates work wonderfully) and cover with mozzarella slices and toss under broiler for 2-5 minutes, until cheese is melted and begins browning.