Put all chocolate in microwavable bowl microwave 30 seconds at a time (approx 2 to 2:30 minutes in a ceramic bowl) chocolate will not be completely melted stir and the rest will melt  (if microwaved to long the chocolate will burn)

once chocolate is melted stir in the peanut butter and vanilla,

finally fold in marshmallows,

line 9x13 pan with wax paper (clean-up is very difficult without it),

spread evenly in pan and refrigerate until firm

This is harder than a normal fudge if you prefer a more traditional soft fudge after adding

the marshmallows slowly add in a 1/2 to whole can of sweeteded condensed milk

(if added before the marshmallows you can't fold the marshmallows in)