KeystoneJS with nunjucks.

nunjucks

//Of course you may want to do more configuration than this.
var app = express();

var env =  nunjucks.configure('/views', {
			autoescape: true,
			express: app,
			tags: {
				variableStart: '<$',
				variableEnd: '$>'
			}
		});
keystone.set('view engine', 'html');
keystone.set('custom engine', env.render);