Thaw shrimp, if frozen. Rinse shrimp; pat dry with paper towels. Set aside.
For garlic paste, cut 1/2 inch off the pointed top portions of garlic bulbs. Remove the outer papery layers of the garlic. Place both bulbs on a square piece of foil. Bring edges of foil together to form a pouch. Seal. Bake garlic in a 375 degree F oven for 35 to 40 minutes or until very soft. When cool enough to handle, use your fingers to press garlic pulp from each clove. Mash pulp with a spoon or fork to make a smooth paste (you should have about 2 to 3 tablespoons). Set aside.
Cook the pasta according to package directions. Drain. Cover to keep warm.
Meanwhile, in a large saucepan cook mushrooms and sweet pepper in hot oil until pepper is tender.
In a small bowl stir together the garlic paste, water, basil, cornstarch, oregano, bouillon granules, and black pepper. Add to mushroom mixture in saucepan. Cook and stir until thickened and bubbly. Add the shrimp to the mushroom mixture. Simmer, covered, about 2 minutes or until shrimp are opaque. Stir in tomatoes; heat through.
To serve, spoon the shrimp mixture over pasta. Sprinkle with Parmesan cheese. Toss to combine. Makes 4 servings.