using firebreath created npapi for chrome can i call the plugin methods from the extensions and not from html loaded page

I've built a simple NPAPI plugin, and registered it with Chrome. This all works; javascript in the browser is able to interact with plugin.

But i need to be able to call methods of my plugin from Chrome extensions.

Can it be done?

Yes, you can. Extensions are implemented in JS and HTML, so you can embed and call a plugin from an extension just as you would from a web page.