To answer the original question: I have never heard this song.

Also, though I think it may be something to do with sugar, I don't really know what molasses is/are.

Or shortening bread, though I have an idea 'mama's little baby' loves it.

I used to think that 'shortening' must be a verb, ie something done to the bread, like pinching the crust from both ends of the loaf because they LIED to you and told you crusts would give you curly hair, then told you off for eating the crusts from each end instead of working your way down the loaf. That 'shortened' the loaf.