Heat 1/2 teaspoon oil in a small nonstick skillet over low heat. Add prosciutto; saute 5 minutes or until crispy. Stir in garlic, turn off heat.
Heat 2 teaspoons oil in a large nonstick skillet over medium-high heat. Add onion and mushrooms and saute 8-10 minutes, or until golden. Stir in tomatoes and cook for 3 minutes. Add spinach and basil and cook for 3 more minutes. Stir in prosciutto-garlic mixture. Cover; keep warm. Season salmon fillets with salt and pepper. Heat remaining 1/2 teaspoon oil in the same skillet used to cook prosciutto over medium heat. Add salmon, skin-side down, and cook, covered 10-12 minutes or until fish flakes easily. Use a spatula to loosen fish from its skin, which will stick to skillet. Divide vegetables among 4 plates, top with salmon and serve immediately