In GroovyFX, how to modularize the page layout?

I'm fairly new to JavaFX and GroovyFX.

I just build my first form on JavaFX, and as soon I got it working I ported it to GroovyFX because I'm on a Groovy/Grails development team.

I'd like to know how to modularize the page layout, that is, how to extract the nodes definitions under the GroovyFX.start() method.

Let's say I have the following simple layout:

start{
    stage(title: 'GroovyFX Hello World', visible: true){
        scene(width: 300, height: 100){
            borderPane{
                center(align: CENTER){
                    text "this is the center region"
                }
            }
        }
    }
}

I can extract code into closures under the start method:

start{

    def renderCenter = {
        text "this is the center region defined in a closure"
    }

    stage(title: 'GroovyFX Hello World', visible: true){
        scene(width: 300, height: 100){
            borderPane{
                center(align: CENTER){
                    renderCenter()
                }
            }
        }
    }
} 

But what I want is:

class CenterRegion {
    def render(){
        text "this is the center region in a separate class"
        // and other stuff
    }
}

start{
    stage(title: 'GroovyFX Hello World', visible: true){
        scene(width: 300, height: 100){
            borderPane{
                center(align: CENTER){
                    CenterRegion.render()
                }
            }
        }
    }
}

How can I accomplish this with GroovyFX?

Thanks

import groovyx.javafx.SceneGraphBuilder
import static groovyx.javafx.GroovyFX.start

class CenterRegion {
    static def render(SceneGraphBuilder builder){
        builder.text "some centered text"
    }
}

start {
    // get the ScenGraphBuilder by getting closure's delegate
    def sgb = getDelegate()

    stage(title: 'GroovyFX Hello World', visible: true){
        scene(width: 300, height: 100){
            vbox {
                borderPane{
                    center(align: CENTER){
                        CenterRegion.render(sgb)
                    }
                }
            }
        }
    }
}