The stretch of Mass. Ave. between Harvard and Porter squares may teem with restaurants and bars, but it’s the laid-back-yet-sophisticated West Side Lounge that draws the locals. The main reason: chef Alex Jenkins’s dinner creations. Available at the bar or in a candlelit booth, Jenkins’s menu includes such straight-ahead appetizers as house-cured olives or grilled pizzas , along with more complex, but still humble, main courses, including roasted chicken, sliced tenderloin of steak, and pan-seared tuna with eye-watering wasabi mashed potatoes and ponzu sauce. The bar provides a solid backbeat, with classic martinis and margaritas, and eyebrow-raising beverages like the “little Debbie,” a thick, liquor-soaked chocolate drink that is definitely not for kids.