Pour broth into small saucepan. Bring to a boil over high heat and reduce to 1 cup. Set aside. Meanwhile, saute mushrooms in oil in a large skillet over high heat 5 minutes, or until golden brown. Reduce heat to medium and stir in garlic. Saute 1 to 2 minutes. Season with pepper. Add yogurt and cornstarch to reduced broth and whisk to blend. Whisk yogurt mixture into mushrooms. Bring to a boil, stirring constantly until thickened. Remove from heat and keep warm. Season salmon steaks with salt and pepper and saute in a lightly oiled non-stick pan over medium-high heat 10 minutes per inch of thickness, or until fish just flakes when tested with a fork. Turn once while cooking. Arrange each salmon steak on a dinner plate with reserved sauce. Serving suggestion: Try this with Garlic Mashed Potatoes and buttered peas.