My son took about two bites of his cheeseburger. Then he kissed it. It was a gentle kiss atop the bun, only half-serious. But this middle-schooler knows a good burger. He meant it. We were having a quick dinner at TwansBurger, a small trailer that’s parked most evenings at Finn’s Manor, an indoor-outdoor cocktail, wine and beer bar at 2927 Larimer St.