I’ve often wondered whether Cajuns engineer culinary oddities just to see if Texans will eat them, and I looked seriously askance at the filet mignon-on-a-stick, $10.95, at Bourbon St. Bistreaux [5555 Morningside, (713)522-9133]. Surprise: This steak snack is actually quite tasty. Admirable chunks of beef tenderloin are cooked to order,…