The Jambo Texan sandwich at Jambo’s BBQ Shack in Rendon. (Photo ©Chris Wilkins/Texas BBQ Posse) Every now and then you run into something so uniquely Texan that you stop in pure amazement. This is the case with pitmaster Jamie Geer’s Jambo Texan sandwich at Jambo’s BBQ Shack in Rendon. The Posse hit Jambo’s in force during their first week of business and was quite impressed. It wasn’t surprising. Jamie not only builds what many consider to be the best BBQ smoker the in the world, the Lamborghini-esque Jambo pit, but he is also a veteran pitmaster on the competition BBQ…