My take on @flashingpumpkin's PizzaBuilder

Builder.scala

case class Pizza(dough: String, sauce: String, topping: String) {
  override def toString: String = {
    "Dough:" + dough + " Topping:" + topping + " Sauce:" + sauce
  }
}

abstract class PizzaBuilder {
  def withDough(dough: String): PizzaBuilder
  def withSauce(sauce: String): PizzaBuilder
  def withTopping(topping: String): PizzaBuilder
  def build: Pizza
}

case class BuildPizza(dough: Option[String], sauce: Option[String], topping: Option[String]) extends PizzaBuilder {
  override def withDough(dough: String): PizzaBuilder = {
    BuildPizza(Some(dough), sauce, topping)
  }

  override def withSauce(sauce: String): PizzaBuilder = {
    BuildPizza(dough, Some(sauce), topping)
  }

  override def withTopping(topping: String): PizzaBuilder = {
    BuildPizza(dough, sauce, Some(topping))
  }

  override def build: Pizza = Pizza(dough.getOrElse("No dough"),
                                    sauce.getOrElse("No sauce"),
                                    topping.getOrElse("No topping"))
}

object PizzaBuilderExample {
  def main(args: Array[String]) = {
    val hawaiianPizza = BuildPizza(None, None, None).withDough("cross")
      .withTopping("ham + pineapple").withSauce("mild").build
    println("Hawaiian Pizza:" + hawaiianPizza)
  }
}

PizzaBuilderExample.main(Array())