Continuing the story...
Dutch Jews did not speak Yiddish as a rule, which isolated them from the larger Jewish immigrant community where it served as a shared tongue. Most made no attempt to learn it either, since there was a greater imperative toward mastering English. So the Dutch immigrants appeared standoffish. In addition they regularly ate tidal seafood like clams and mussels, which weren't kosher. So they didn't seem all that Jewish. The other Jews called them "chuts", which wasn't derogatory apparently, and translates as "happy".
They wouldn't say much. Just smile.
Having had no luck at the cigar factories, I tried Sandys Row Synagogue, another venue where the Sasieni and Elkan families might have forged a lasting relationship. Its founders were a group of fifty families of Dutch Jews from the Tenter Ground, who were determined to establish a synagogue of their own in London's East End. The participation of the Sasieni family seemed likely. I tried a few searches using the various spellings, and actually found something: a newsletter from the London Chorale Society dated 1875, which announced that a Moses Sassieni of 16 Freeman Street had applied for a paid position as a tenor in the choir of Sandys Row Synagogue, of which he was already a member, at the stipend of five pounds per annum.
The synagogue formally opened to the public in 1880, and its doors haven't closed since. I visited their website, which has a database of marriaige records covering this period, and found matches for both Sasieni(55) and Elkan(27). I balked at making an advanced search however. This required a substantial donation. Enough to buy a couple of nice briars, unfortunately. I was really looking for their membership records, anyway. After searching through the Sasieni census documents, I felt certain that there had been no intermarriage between the families.
Although founded by families of Dutch Jews, the congregation quickly grew to include Poles, Russians, and Germans - the entire Jewish community - with their membership roll topping out around 450 families. Services were held in Hebrew, and all Jews were equal. It became a revered institution among the working class Jews in Whitechapel, and as a result of fundraising for its charitable work, I suspect that the Elkans would have come under considerable pressure to support Sandys Row Synagogue as well. I have a hard time imagining them wanting to spend their Sabbath in the squalor of Spitalfields, though. They might have paid membership dues as a way of making a donation, but never attended services.
Even if I were able determine that Alexander Elkan, Baron Elkan, Albert Bessie, or Stanley Phillips were on their membership list, would it prove anything?