Go to the 'food court' at Galleries Lafayette. It is a market plus there are some ready-made items. A few of the purveyors have a place to sit down and eat. Lots of provisions to buy. Wonderful pastries, I adore the green tea dome from Aoki. Get some Bordier butter to have in the mornings. Take a break from restaurants.
Go to Jacques Genin's pastry shop / tea salon. Exquisite, and I have a special fondness for the lemon basil tart which is unbelievable.