Early, I presume you are looking for non steak-house Steak Frites - otherwise Barberian's and the other usual suspects would clean up.
Amongst the bistros:
On a good day, the steak frites at Le Petit Dejeuner are as good as anywhere.
La Pallette used to be great but they changed their sauce a few years back.
Batifole is also good but I don't like the bone marrow taste of the sauce.
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