Muriel's Peanut Butter Fudge

Mad sent me this recipe and it sounds GOOD. I've never made peanut butter fudge before so now I have something new to look forward to for Christmas.
Mix in a saucepan:
1 cup white sugar
1 cup brown sugar
3/4 cup Carnation Evaporated Milk
1/4 cup butter
Boil together until it's at the crackling point (roughtly five minutes.). If you have never made candy before, I am too faint-hearted to instruct you in how, but it IS doable. But tricky - as Mad warned in her email: "It's all about seeing and hearing the right moment. If you take the pot off the stove too soon you have runny fudge. If you leave it a minute too late, your fudge is too hard to work with."
Let cool for a minute and then beat with an electric mixer.
After about a minute, stir in 3/4 cup peanut butter and a tsp. of vanilla. Spread into a greased 8" pan. Let it cool and then cut into squares.
(Mad also added that you could add walnuts or coconut. Well, you could. Stir them in at the same time as the peanut butter and vanilla, if you must.