Toasted Marshmallow and Rhubarb Cake

This is a relatively new addition to my rhubarb repertoire, but it has been heavily in rotation ever since I first made it nearly two years ago. Anyone who has a birthday when the forced pink rhubarb is in season gets it (and I do even have alternatives for those dim days when it isn’t, and I’ll get to them later). It is splendidly celebratory, but not dauntingly difficult. You need a bit of elbow grease and a blowtorch; I can’t tell you how much I enjoy teasing out the snowy spikes of mars