It occurred to me that it might be helpful to document how I prepare senposai for cooking, to show how easy it is, much easier than any other green!
How to Clean and Prepare Senposai
First, I rinse each leaf under running water, removing any dirt caught in the center rib. The leaves are flat and easy to clean.
I stack the rinsed leaves in my salad spinner. One full 'load' is the right amount for 4 servings.
If the leaves are really dirty, I will fill the spinner and give them a second rinse. If they're clean, as they have been, I spin them dry.
Next, I remove the center rib. For some recipes I reserve the ribs, for others they go on our compost pile.
The plants are young now and the leaves fit easily in my spinner. As the leaves get bigger, I remove the ribs before I spin the leaves, and I cut the leaves in quarters so they'll fit in the spinner.
Compare this process to cleaning curly kale for instance - I rarely cook curly kale because it's so hard to get the dirt out of the crevasses! The only green that's almost as easy to clean as senposai is russian kale which is also flat and mostly crevasse free, except for the ruffles around the edges.
Most of my recipes call for chopped senposai.
Once I've removed the ribs, I stack the leaves according to their size. The smaller leaves I cut in half lengthwise and stack both halves. Then, I slice them (this is much easier with a very sharp knife!) crosswise.
The larger leaves I quarter lengthwise, stack all four, and then slice them crosswise. If the leaves are really big, cut them into 2" strips.
Once all the leaves are sliced crosswise, I chop the mound into roughly 1" pieces.