Clare,
Well I have a very old version of Betty Crocker Cookbook and I see
two that might be what you want.one is called
Cream Filling
1/3 cup granulated sugar
3 Tablespoons all-purpose flour
1/4 teaspoon salt
1 1/4 cups milk
1 beaten egg
1 Tablespoon butter
1 teaspoon vanilla

In saucepan, combine sugar, flour and salt. Gradually add milk; mix well.
Cook and stir over medium heat till mixture thickens and boils; cook and
stir 2 minutes longer. Very gradually stir the hot mixture into the egg
return to saucepan. Cook and stir till the mixture just boils. Stir in
butter and vanilla; cover surface with waxed paper or clear plastic wrap.
Cool(Don't stir during cooling) Makes 1 1/2 cups.

another one...

FRENCH CUSTARD FILLING

1/3 cup sugar
1 tablespoon all-purpose flour
1 tablespoon cornstarch
1/4 teaspoon salt
1 1/2 cups milk
1 slightly beaten egg yolk
1 teaspoon vanilla
1/2 cup whipping cream, whipped

In saucepan, combine sugar, flour, cornstarch and salt. Gradually stir in
milk. Cook and stir until mixture thickens and boils; cook and stir 2-3
minutes longer. Stir a little hot mixture into egg yolk; return to hot
mixture. Cook and stir till mixture just boils. Add vanilla; cool.
Beat smooth; fold in whipped cream.

Hope one of these is it.

Tami