This recipe is from a the 1844 cookbook, The Lady’s Own Cookery Book and Dinner Table Directory.
Beat sixteen eggs very well in a wooden bowl, leaving out six whites, with a little orange-flower water and brandy; then add to them by degrees half a pound of fine sifted sugar; grate in a nutmeg, and a quarter of a pound of Naples biscuit; add a pint of the juice of spinach, and four spoonfuls of the juice of tansy; then put to it a pint of cream. Stir it all well together, and put it in a skillet, with a piece of butter melted; keep it stirring till it becomes pretty thick; then put it in a dish, and bake it half an hour. When it comes out of the oven, stick it with blanched almonds cut very thin, and mix in some citron cut in the same manner. Serve it with sack and sugar, and squeeze a Seville orange over it. Turn it out in the dish in which you serve it bottom upwards.
If you can get your head around ye olde English here is a great recipe for Tansy cake. It was first published in Liber Cure Cocorum 1430. I’m pretty sure a skillet is needed, beyond that you are on your own!
Breke egges in bassyn and swyng hem sone,
Do powder of peper þer to anone;
þen grynde tansy, þo iuse owte wrynge,
To blynde with þo egges with owte lesynge.
In pan or skelet þou shalt hit frye,
In buttur wele skymmet wyturly,
Or white grece þou make take þer to,
Geder hit on a cake, þenne hase þou do,
With platere of tre, and frye hit browne.
On brode leches serve hit þou schalle,
With fraunche mele or oþer metis with alle.