Example for handlebars, but this should work for any template engine that takes helpers or filters.
var handlebars = require('handlebars');
handlebars.registerHelper('frame', require('{%= name %}'));
var fn = handlebars.compile('{{#frame site=site}}Name: {{@site.name}}{{/frame}}');
console.log(fn({site: {name: 'Test'}}));
//=> 'Name: Test'