Can't stop a defined recursive function using Scala

I have the below function which i can't stop from looping and don't understand where i'm going wrong.

def takeSingleTableDrinkOrder(size: Int): String= {

var order = ""

if (size == 0) order  = "finish"

else order = {

     println("\nHow old are you?")

     var age = readLine.toInt

       if (age < 18) { 

         println("\n\nchoose from the following:\n\n"  
         + "pepsi\n"  
         + "coke\n" ) 

   var input = readLine
   input

  } else {

       println("\nchoose from the following:\n\n"  
       + "pepsi \n"  
       + "coke \n" 
       + "wine \n" 
       +  "beer\n")

  var input = readLine
  input
  }

}

 val drinkOrder = order + ":" + takeSingleTableDrinkOrder(size - 1)

  drinkOrder    
}  

I'm new to Scala so please excuse my simple questions.

Thanks