I think the red currant jelly is an excellent guess @greygarious and it led me to think that this childhood tart may have been a tarte tatin with pears instead of apples; also wondering if “the whiskey” could have been calvados, considering your mom’s French heritage @Kspa2019 . The tart too of course.
I searched for “French Pear Custard Tart” and several recipes come up that look similar to what you describe - shortcrust base, sliced pears, egg custard or creme patissiere, and a final glaze of jam or preserves.
It’s possible that your mom adapted a recipe to her/your family’s taste, rather than followed a single one - so if you backsolve from the parts you remember - an English or French shortcrust base recipe, a simple custard, and then raw or canned or poached pears sliced up, and a final glaze - you might be able to create your own (memory) version of mom’s recipe.
Thank you all for the recipes and suggestions. I’ll be trying them. But keeping my fingers crossed… still hoping someone will have the recipe…
London in the '80s, the “batter” could have been something as simple as clotted cream. Maybe a little sugar added.
Here a substitute might be creme fraiche or Mexican sour cream, or commercial sour cream thinned with a little sweet cream, half and half.