Easy Beef Stroganoff

Ingredients

• 2 tablespoons butter
• 2 tablespoons olive oil
• 1 lb fresh mushrooms
• ⅓ cup white wine
• 2 cups beef stock
• ¼ cup sour cream
• 3 tablespoons all-purpose flour
• 2 teaspoons dry mustard
• Salt and pepper
• Fresh parsley
• 1½ lbs beef sirloin steak
• 1 large onion
• 2 garlic cloves