somewhere to pick up something tasty to take on Eurostar.
Nothing to do with food, but normally you only have to get to the Eurostar terminal a half hour before.
Anyway, a 5/10 minute walk away from the Gare du Nord (or get off the metro (line 4)) at Strasbourg st denis, or chateau d'eau), you have the rue du faubourg St denis.
Whereas the Mortogeueil or Mouffetard neighbourhoods have a kind of Disney/ museum quality to them this street is more contemporary. Some people, or rather journalists, like to call it "little Istanbul", which is an inaccurate monkier as most of the "Turks" here are actually Kurds - it's probably one of the few ethinic-chic neighbourhoods on the planet where americans are actually welcomed.
You have all of the Kudish places, including, in my opinion Urfa Durum. From a previous post : "On the even numbers side of the street, from the corner of the rue chateau d'eau you go about 20 yards towards the triumphant arch at the end of the street, is Urfa Durum, for the best Kurdish Pizza (i've tried all of the numerous Kurdish pizza joints in the 'hood) Here, they're stuffed with lettuce, parsley, tomatoes and mint. If you want these pizzas at their most crispy, it's best to eat them "sur place", sitting on the funny chairs at the funny tables. They also do really good kurdish sandwiches; the best, for me, being the lamb's liver. If you're thirsty and your French is rusty, point to the bowl of homemade drinking yoghurt at the end of the bar."
IOn the other side of the street, on the corner of, I think, the rue Echequier, is Chez Jeanette.
This place, especially after 8pm and on weekends, is becoming fuller and fuller. The décor is decadent and fantastic, and the French food, and prices, for the daily specials at least, are really good. You can also just go and have a coffee.
The serviice is a bit "Gallic" at times, but for cheese and wine (they do good sandwiches to go) check out at No 60, Julhes. They have patés and cheeses and wines for all budgets.
You didn't mention either which Gare you are leaving from or where you are staying, so helping you out is tough. So, what we did was to buy bread, cheese, some ham or turkey, a little mustard, some fruit, and a bottle of red (have someone nearly uncork it for you and find some plastic glasses at Stabucks when you get some coffee) from any of the many monoprixs or other small stores and some pastry from a bakery. Some small salads, olives, cous cous, etc are nice, too. Give us the other info and we can direct you to the better shops. Consider it a picnic! The trains are far simplier than the airlines, as someone above points out. 30 minutes before departure is an ample amount of time for arrival. Once we traveled first class and the food was "upscale" TV dinner and ample coffee, wine and juice. Economy is nothing, unless you buy on the train and those prices are rediculous and the food is awful.
Did you ever make it to Hidden Kitchen?