In a 2 quart saucepan over medium heat, melt butter the stir in the flour. Stir the 2 together into a paste. Whisk in the milk to create what the French call a bechamel sauce. Drop the temperature a little and simmer the sauce for about 10 minutes so it thickens and the flour taste cooks out. After that it's easy, just fold in the crumbled feta, scallions, and parsley. Season it with salt and a little cracked pepper.
Once the cheese melts it is officially fondue, you can either use a fondue pot with a candle or just leave it in the pot and have everyone eat from there.
Finish it with the walnuts tossed on top. I like to cut up bite size pieces of bread and melon or maybe pitted olives and prosciutto, either way this is always a holiday hit.