I'm just wondering what the difference between the two are, and whether you can substitute between the two? My recipe for sticky toffee pudding calls for treacle but I only have molasses. Can I substitute the treacle for molasses? It is kinda hard going to the shops just at this moment?
Here is a good article explaining the different types of molasses.
True treacle dates back to Victorian times. The pale, refined molasses is notably sweeter and has a much more mellow flavor than molasses. Nowadays, treacle is a blend of molasses and refinery syrup. It ranges in color from light gold to nearly black. British treacle can be substituted for molasses in most recipes, but much less frequently will molasses work as a replacement for treacle. If you do substitute molasses for treacle, use the lightest, unsulphured molasses you can find.
Treacle is a more general term meaning a syrup formed during the sugar refining process. It can range in color and consistency. Black treacle is molasses, but there are lighter versions of treacle. Of course, the flavor profiles will be different depending on the type of treacle. For toffee pudding, the use of molasses will work, but the flavor will probably be heavily influenced. I've see recipes that use light corn syrup, Lyle's golden syrup, or even brown sugar. That tells me that lighter versions are probably more typical.