Butter sides of a heavy 3 to 6 qt. pan.
In it combine sugar, milk, and butter.
Cook over a medium heat to soft-ball stage (236º) (use a candy thermometer), stirring frequently.
Remove from heat, add chocolate chips, marshmallow creme and vanilla.
Beat until chocolate is melted and blended.
Add walnuts just before pouring.
Pour into a buttered 9"x13" pan.
1) Butter sides of pan
2) Stir fudge until it comes to a boil and all the grains of sugar are dissolved. Sugar will dissolve easily at this stage but can't after mixture concentrates. One sugar crystal can start a chain reaction and make the entire batch of fudge grainy. Wait to clip on candy thermometer until mixture boils.
3) Check temperature of fudge often after it reaches 220º. It will climb fast after this point.
4) After candy has cooled undisturbed to 110º (bottom of pan should feel comfortably warm to your hand), add vanilla and start beating vigorously.
5) Pour fudge at just the right moment - fudge will seem to stiffen and loose its gloss. This is also the time to add the nuts. Push mixture from pan with rubber spatula.
6) Score fudge while warm for neater squares, using tip of knife. Dip knife if water when necessary.