Sure, Roy Allen and Frank Wright are better known for the exquisite root beer concoction sold first from California drive-up stands under the A & amp;W brand name. But these days the company makes a darn good vanilla cream soda as well. And the formula is one we can easily clone at home by combining a few simple ingredients. Most of the flavor comes from vanilla, but you'll also need a little lemonade flavor Kool-Aid unsweetened drink mix powder. This mix comes in .23-ounce packets and…