This class will demonstrate the kotlin features along with building a Pizza DSL.

Pizza.kt

enum class Cheese{Light, Normal, Extra;}
enum class Sauce{Marinara, GarlicParmesan, Alfredo}
interface Topping
enum class Veg: Topping {Onion, Tomato, Pepper, Spinach;}
enum class Meat: Topping {Chicken, Pepperoni;}

fun main() =
    pizza {
        large {
            add(Sauce.Alfredo)
            add(Cheese.Extra)
            toppings {
                add(Veg.Tomato, Veg.Onion, Meat.Chicken)
                half{
                    add(Meat.Pepperoni)
                }
            }
        }
    }.order()

fun pizza(build: Pizza.() -> Unit): Pizza{
    val pizza = Pizza()
    pizza.build()
    return pizza
}

class Pizza{
    var size: String = "Medium"
    var sauce: Sauce = Sauce.Marinara
    var cheese: Cheese = Cheese.Normal
    var toppings: MutableList<Topping> = mutableListOf()

    fun large(size: Pizza.() -> Unit){
        this.size = "Large"
        this.size()
    }
    fun medium(size: Pizza.() -> Unit){
        this.size = "Medium"
        this.size()
    }
    fun toppings(tops: Pizza.() -> Unit) = this.tops()
    fun half(side: Pizza.() -> Unit) = this.side()
    fun add(sauce: Sauce) : Pizza {
        this.sauce = sauce
        return this
    }
    fun add(cheese: Cheese):Unit{
        this.cheese = cheese
    }
    fun add(vararg toppings: Topping) = this.toppings.addAll(toppings)
    override fun toString(): String{
        return """Pizza [
    $size [
        Sauce: $sauce Cheese: $cheese
        $toppings
    ]
]"""
    }
    fun order() = println(this)
}