Using the same pan melt the butter and begin to slowly add the tapioca flour. Whisk constantly. At first the tapioca will look like it is starting to gel. This is normal. It does not behave like flour until later in the process. Slowly add 2 cups of milk and continue to add the tapioca flour and continue to whisk. Add the salt and pepper and keep whisking. This will get very think, don’t panic, it’ll be fine.