Best pratice to insert string into HTML file using node

Suppose I have a large HTML-file, and at a few places I want to insert a string, which content is set during startup. How would I solve this if I'm only allowed to deliver a static HTML, hence everything has to be handled on the server-side.

You can use JADE templating engine. If it will be static all the time, you can compile the templates to your public directory and serve them with a framework like ExpressJS

If you already have this HTML file, I would suggest use of EJS.

Rewriting anything to haml (jade) is just too much work...