If your sweet tooth has already overpowered your New Year’s resolutions, then a trip to Harvard Square may be in order. Through February 28, both Somerville Chocolate (somervillechocolate.com) and Gâté Comme des Filles (gatecommedesfilles.fr, pictured) temporarily take over the seasonally shuttered Lizzy’s Ice Cream (29 Church St., Cambridge, 617-354-2911). Normally headquartered at Aeronaut Brewing Company in Somerville, both confectioners are now offering gourmet treats to Cambridge customers in what has been dubbed Somerville on the Charles. That means that visitors to the square can pick up Gâté Comme des Filles’ tempting truffles, chocolate mousse and the like and Somerville Chocolate’s bean-to-bar creations seven days a week.