Preheat oven to 350°F. Mix cornstarch, basil and onion salt in small bowl. Set aside.
Melt butter in large skillet on medium-high heat. Add onions; cook and stir 6 to 7 minutes or until golden brown. Add mushrooms; cook and stir 2 minutes or until mushrooms are tender. Stir in cornstarch mixture. Add milk and soy sauce; stir constantly, cook until sauce is thickened and bubbly. Add cream cheese; cook and stir until cream cheese is melted. Add cooked green beans; toss gently to coat.
Spoon into 2-quart baking dish. Sprinkle top evenly with almonds.
Bake 25 minutes or until heated through and top is lightly browned.