Middlesex's Filling Station has closed after a brief stint as a barbecue joint. This winter, owner Brian Lewis' former sous chef, Andrew Lay, will take over the revamped service station to open Chico's Tacos & Bar. The native of Orange County, Calif., will serve what he called "California-style Mexican fast food," including burritos, carne asada, carnitas and fish tacos. The counter-service spot will have a full bar, offering margaritas plus local and Mexican beer. Lay worked for Lewis earlier in his career in California, as well as at Filling Station and Montpelier's Filibuster Restaurant & Bar. He's targeting a late December or early January opening for his first restaurant as chef-owner. "I thought I'd bring a little piece of home with me," Lay told Seven Days. "We'll stick with the classics and do them really well." Lewis said sales had been dropping at Filling Station since May. Add staffing issues, and "the cost of keeping it open became prohibitive," he said. Lay's owner-operated model will "make for a more profitable business," in his view. Meanwhile, the second location of Lewis' Yellow Mustard deli and sandwich shop opened in the former Perky Planet space at 170 St. Paul Street in Burlington on Monday. The menu offers all the same sandwiches, panini, wraps and salads as the original in Montpelier. Lewis plans to open a third Yellow Mustard in Williston's Taft Corners by March and hinted at more locations to follow. "Everyone loves a sandwich, and, especially in today's market, people appreciate value," Lewis said…