I love it when I find a treasure that someone has thrown away, not seeing its beauty. That's how I feel about spinach hearts. Some people call them crowns or feet, but most people call it the part that gets thrown away. It's the stem clusters at the bottom of the spinach plant.
In Japan, this dish is called Horenso No Neno Goma-Ae.
There is a wonderful book, now out of print, written by Soei Yoneda (High Priestess of the Sanko-in Temple). This recipe and many other beautiful, simple recipes are in this book. If you browse used book stores, watch out for this treasure of a book.
I think of preparing the spinach hearts as a meditation. One needs to make sure all of the grit is removed and that while removing the leaves for another purpose, one preserves the beauty and integrity of the heart. Once prepped, I always let the hearts sit in a bowl covered with a damp cloth over night (or for a few nights....you can keep them in the refrigerator in a container if you want to. I keep mine on the counter. The hearts open joyfully.
It was always curious to me to find that the Japanese serve spinach cold. The leaves are usually blanched quickly, plunged into ice water, squeezed into a block, then the block of spinach is cut into slices.
The hearts, too, in Soei Yoneda's recipe, were blanched for a couple of minutes, then took the ice water plunge. They certainly retain more of their crisp beauty that way, and for a summer dish, I'd do that too. Right now, I'm more interested in a hot dish because almost everything else I eat is cold, so I'll sacrifice looks for warm food. Wilty, but warm and still delicious.
4 tbsp raw tahini
2 tbsp tamari
2 tbsp mirin (Japanese rice vinegar)
2 tbsp sake (or not...it's up to you)
I make a much larger batch than this because it's also delicious with cooked grains and as a basis for salad dressing. Whisk until smooth. Add a little water if it's too thick. (Some tahini is thicker than others).
You'll need more spinach hearts than you think because they cook down, even when you only blanch them briefly. I usually plan a "spinach week" where I'm using spinach two or three times for other things. (Not hard when you are drinking a lot of green smoothies ). I collect all of the hearts for this dish, and it's a treat.