Heat 2 tablespoons of light olive oil over medium heat in a heavy-bottomed skillet, and cook the diced tomatoes and garlic for about 8 minutes or until they become soft and juicy. Transfer them to a bowl and set aside.
Wipe the skillet with a paper towel and heat one more tablespoon of olive oil over medium-high heat. Saute the onions and mushrooms until the onions are caramelized, about 4 minutes, and return the tomato mixture to the skillet.
Add the sour cream, oregano, red pepper flakes, salt, and pepper to taste.
Pour in the chicken broth and white wine.
Bring the sauce to a simmer and cook until slightly thick. Add the shrimp and let them cook for one minute. Turn them over, and cook on the other side for 2 minutes more. Serve over white rice, pasta, or mashed potatoes and freshly chopped parsley on top.