I’ve often taken Marmite and Branston Pickle, etc. to a sister in the US. I’ve always declared them, but did once have a job explaining to the customs bloke what Marmite was. ‘Something you put on toast’ didn’t seem to get through, but eventually he said, ‘Is it jam?’ So I said yes for a quiet life. I dare say his ideas of jam were hazy anyway, since Yanks usually call it jelly.
Another time, decades ago, DSis and BiL were running a small gift shop in Provincetown (Cape Cod) so I took about half a kilo of frankincense, since we were living at the time in Oman, where it grows, and was available by the sackful in the souk.
So I declared it, in case the customs bloke thought it was freeze dried crack or something (it looks a bit like those old fashioned coffee sugar crystals you used to get) - but after a while the poor chap’s eyes glazed over and he waved this mad Brit woman through.?