dsl.kt

class HTML {
    fun body() { ... }
}

fun html(init: HTML.() -> Unit): HTML {
    val html = HTML()  // create the receiver object
    html.init()        // pass the receiver object to the lambda
    return html
}

// Call `html` and pass lambda to it. Inside the lambda we can call `body` directly thanks to the usage of a receiver. 
html {       // lambda with receiver begins here
    body()   // calling a method on the receiver object
}