Here’s an interesting article about how to translate “Pork Pie Plot” into other languages, especially in the context of headlines. The PPP is an attempt to unseat Prime Minister Boris Johnson (who, incidentally, is descended from one of the best-known and most controversial German-to-English translators, Helen Lowe-Porter).
With regard to headlines, two questions come up here: 1. Should you use these kinds of quirky foreign phrases in headlines? And 2. If you do, should you translate them or leave them in the original language?
My answer to (1) would usually be yes, because it’s an attention grabber. The answer to (2) largely depends on what the two languages are and whether the speakers of the target language tend to be familiar with the source language. You might include Spanish in a US newspaper headline but you wouldn’t do the same with Mongolian. It also depends on whether the target language has a clear equivalent. I googled “torta di maiale” and found that Italy seems to have pork pies that look a lot like the British ones, so sure, go ahead and translate “the Pork Pie Plot” as “il complotto della torta di maiale.” Google Translate is a little confused about this food item, though:
At least they didn’t call it Porkpiegate, which is what it would be over here.