Hot Chocolate
Ladurée is known for their lovely macarons, but their hot chocolate is also delicious. Many locations throughout Paris
https://www.laduree.fr/en/our-shops-and-restaurants.html
Many have recommended Angelina's (226 Rue de Rivoli). I've never been, however.
For Steak Frites, go to Le Relais de l'Entrecôte. There's only one thing on the menu (but many dessert choices... I recommend the crème brulée). Excellent food and service.
Open for lunch and dinner. Never been for lunch, but for dinner they do not take reservations. If you don't want a long wait, the Pro Tip is to queue up about 6 pm (or earlier), before they open at 6:45 pm. (Or, you can go later if you want a late dinner.) If there's already a long line when you arrive, just get in it and hang tight. Once they open, the line moves quickly.
There are 3 locations, including one in Saint Germain (Rue Saint-Benoît, near Église Saint-Germain-des-Prés), which we've dined at twice (most recently May 2023). I have no experience with the other locations.
https://www.relaisentrecote.fr/?page_id=205&lang=en_GB
Consider Galeries Lafayette for an iconic and over-the-top Parisian shopping experience. Do NOT go there if you are sensitive to perfume. It is ubiquitous as soon as you walk in the door. Near The Opera Garnier, an exquisite piece of art unto itself.
Bon Appétit