Ended up at Belleville on Friday night. The interior is a more spacious version of Moutarde. Not sure if Park Slope NEEDS another French bistro, but my experience was pleasant enough (a good sign for their first week of operation). Still BYOB, and no credit cards yet.
Items consumed amongst a party of five:
> French onion soup -- I tasted this. It was pungent and not too salty.
> Mixed green salad -- HUGE and only $6.50
> Organic grilled chicken -- I tasted this too. Very tender and juicy
> Grilled tuna -- didn't try this, but it's orderer was pleased
> Monkfish -- didn't try this either
> Mussels and fries (mine). For $13.50, I won't complain about this sizable bucket of mussels. Broth was a tad on the salty side. Fries were also tasty.
> Chocolate torte with pistachio ice cream. Perfect for sharing. The pistachio ice cream was fantastic.
All in all -- a good neighborhood spot. Not a Chowhound spot, but reasonable and tasty. My advice to the owners would be stay BYOB, which I know they won't.