Parsley grows on a single stalk if you are talking about the herb Curly parsley. Did you sow seed and when you split it, it would be like potting on annuals where you just tease the roots apart. It is flowering because it thinks its time to set seed to propagate itself. You should always cut parsley taking the full stem not just the green curly bits. If you cut the flowering stem back to the base it might continue to try to flower or it might give you some edible leaves. Your alternative is to chuck these out and sow some fresh seed - good tip - water the planting row with boiling water before you sow the seeds or soak the seed overnight in hot water, it will cool but parsley seems to need that heat to get going. Thin out your new plants to give them a good chance of growing well. You can put one plant in a six inch pot which can be brought in to sit on the kitchen window sill over the winter. I have also been successful in buying a small pot of parsley in a supermarket, on the veg counter, and transplanting individual plants from that. The pot is too small to successfully sustain the needs of the many plants contained in it. Good luck.

As said above, parsley is a biennial, grows one season and flowers the next, so something you transplanted in November is now into its second year and it is normal to flower.
As suggested, let it self seed or collect the seed and sow it somewhere for new plants later this year and early next.

Thanks S. and B. I guess I've got it wrong again ! They say " learn from your mistakes" and I'm certainly doing that - often !

You will soon learn that the more you know the more there is to learn. Join the club.