var myTemplateName = 'someTemplateName';
var myTemplateVariableData = {myTemplateVariableData: {'xxx': 'some data}};
var myTemplateHTML = Template[myTemplateName].render(myTemplateVariableData);

var myTemplateVariableData = {'xxx': 'some data};
var templateName = 'someTemplateName';

var myTemplateHTML = "";
var dr = new UI.DomRange; // domain range

var loadedTemplate = Template[templateName].extend(
    {
        data: function () {
            return { myTemplateVariableData: myTemplateVariableData }
        }
    }
);

var renderedTemplate = loadedTemplate.render();

UI.materialize(renderedTemplate, dr, null, dr.component);

for (var member in dr.members) {
    if (dr.members.hasOwnProperty(member)) {
        var testHTML = dr.members[member].innerHTML;
        if (testHTML) {
            myTemplateHTML = myTemplateHTML + testHTML
        } else {
            myTemplateHTML = myTemplateHTML + dr.members[member].textContent
        }
    }
}

{{#if myTemplateVariableData.xxx}}<span>&nbsp;{{myTemplateVariableData.xxx}}</span>{{/if}}