Let’s get one thing out of the way: Burgos is not a city short on hearty, old-school Castilian cooking — morcilla, lechazo, thick red wines, the works. So when a restaurant in the historic center decides to zig where everyone else zags, you notice. La Fabrica Restaurante is that zig. Tucked just off Calle San Juan, a few minutes’ walk from the Museo Histórico Militar de Burgos, it’s the kind of place where a menu del día can share a room with wagyu meatballs and celery ice cream, and somehow nothing about that feels like a gimmick. I went in with reasonably high expectations — La Fabrica Restaurante has picked…