I bought some prune plums to make this, however after being left on the counter, the plums are still not sweet. Should I make the torte anyways, perhaps grill the plums first, or look for a sweeter plum.My friends are looking forward to this!
Roast them! With a little sweetener. Here's a temp guide: https://food52.com/recipes...
I made this with slightly underripe plums about a month ago, and it turned out great! the plums turned juicy and sweet while it was cooking. i wasn't expecting that to happen, but i was pleasantly surprised!
I have observed the same thing with a different plum cake recipe. The Italian prune plums were nothing special to eat out of hand but cooked with a sugary topping they turned delicious.
I would wait 2-4 days (check everyday) more while leaving them on the counter, in paper bag, mixed with 2-3 apples. Warmer areas (like under the windowsill) also make them ripe faster.
Make it! It will still taste delicious. Use the slightly higher amount of sugar - I think she adjusted the recipe over the years to reduce the amount - the original has a range of 3/4 to 1 cup.
I've been making this for decades, with all degrees of plum ripeness - never fails. Raw prune plums are usually kind of meh; baking brings out their essential pluminess.