Blancs-Manteaux ("White Coats")? Monks from Saint-Augustin order, who used to wear white clothes. They came from Marseille, and moved here in Paris in order to found a monastery, a chapel and a cemetery in 1258, allowed by king saint Louis.
In 1274, pope dissolved the order and other monks from Saint-Guillaume in Montrouge (near Paris) came here in 1297. Their own clothes were... black! Fear not, they kept the name of Blancs-Manteaux... 3 centuries later, those monks left and Benedictines from Saint-Maur replaced them. The French Revolution soon expelled them from the convent...
The former chapel, dedicated in 1397, was replaced by the current chapel in 1685, raised by Antoine de Machy: parents of the future Louis XIV’s minister, Louvois, laid down the first stone! The convent closed during the Revolution.
About 30 years later, the famous Victor Baltard added a bay to the nave and an 18th century portal to the façade. Oh, a portal which came from Barnabites church in the Cité island, destroyed during Haussmann's huge building site!