Pronounced pretty much the way you'd expect. Long e. trE'cl

Are treacle & molasses interchangeable in recipes? From what I found in OED, I think treacle might be sweeter, but it's not clear.

I found this distiction at OED:
treacle: a. The uncrystallized syrup produced in the process of refining sugar; also sometimes extended to the uncrystallizable syrup that drains from raw sugar; = MOLASSES

Note to molasses: In technical language, molasses is applied to the drainings of raw sugar and treacle to the syrup from sugar in the process of refining.

Oh sorry! Did they turn to sugar as a source for treacle after the mines were worked out?