Mashed potatoes and gravy might be tasty, but at what price comfort food? That’s a question the Department of Public Works (DPW) is putting to the District’s Boston Chicken/Market restaurants. In the past year, DPW’s sanitation inspectors have fined three outlets for grease-control violations. On Sept. 15, DPW inspector Tom Day cited the Adams Morgan branch for using illegal 55-gallon drums to store grease in the alley behind the eatery. According to the $50 citation, the drums were filled with “waste cooking oil, spilling out onto public space, causing slippery conditions and feeding rats.” Earlier this year, Day says, the Glover Park Boston Chicken was cited because its rear storage space resembled a grease slide. The store promised to remedy the problem with a special anti-grease steam cleaner. But the most violent crise de la graisse, says Day, arose last winter at the Dupont Circle Boston Chicken. Grease backed up in the drains, says Day, causing a volcanic eruption at the restaurant and at its Connecticut Avenue neighbors, a nightclub and cookie store.