Old Fashioned Beef Stroganoff

Ingredients

• 1 1/2 lbs chuck roast, trimmed of fat
• salt and pepper, to taste
• 1 1/2 cups onions, coarsely chopped
• 1 garlic clove, minced
• 2 tablespoons olive oil, divided
• 2 tablespoons butter, divided
• 32 ounces beef broth (I use Swanson's)
• 1 tablespoon soy sauce, less sodium
• 6 ounces sliced portobella mushrooms, coarsely chopped
• 4 tablespoons cornstarch
• 1/8 cup sour cream, heaping