Pre-heat oven to 400°F. Slice tomatoes in half, and scoop out insides; set aside. Sprinkle cut sides with a small amount of salt and place over a rack, cut side down, to drain.
Heat skillet over medium-high heat; add oil; swirl. Add sausage and begin to brown. Separate out as many tomato seeds as possible and discard. Chop tomato insides. Add to sausage pan along with onions and garlic and sauté for one minute. Add mushrooms and sauté 2 to 3 minutes longer. Add rice; sauté until all ingredients are cooked tender; about an additional 3 or 4 minutes. Deglaze pan with white wine and cook off excess. Add pepper, taste and adjust seasoning.
Stuff tomato bottoms with rice mixture; top with cheese and a sliced mushroom. Stuff tomato tops with cheese. Place all in a small enough pan to keep them as upright as possible and into oven to bake until cheese is melted, golden and bubbly. About 10 to 15 minutes. Serve each tomato bottom with a cheesy top.