This recipe isn't the one you want but sounds close.
It's from Farm Journal's Complete Pie Cookbook.
Can you remember the name of the cookbooks you sold?
Maybe someone has the set.
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Custard Crunch Mince Pie

Unbaked 9” Pie Shell
1 cup Sugar
2 Tbsp. Flour
1/8 tsp. Salt
3 Eggs, slightly beaten
1/4 cup Butter or Margarine, melted
1/2 cup chopped Walnuts
1 cup prepared Mincemeat

Blend dry ingredients and slowly add to eggs.
Add remaining ingredients; mix well.
Pour into pie shell and bake in hot oven (400° F.) 15 minutes.
Reduce heat to 325° F. and bake 30 minutes