I’ll start with a perennial favorite: the Spinach-Rice Casserole from the New Moosewood Cookbook (p. 135). It’s quite flexible, but I think the nutmeg & cayenne give it a particularly nice flavor. Kale works ok if you cook it down, but I tried it once with mustard greens and it was not tasty. Freezes ok, if you don’t nom it up right away! Vegetarian as written, and you can eliminate the dairy, for a vegan version (though you may want to add something binder-y).
The basics:
Saute 2# spinach with some onion, salt and garlic. Mix into 3c. cooked rice. Add 1/4t. nutmeg, 1/4t. cayenne, 1/2c. sunflower seeds. If you like, beat 2 eggs with 1c. milk, and add to the rice mixture. Mix in 1 1/2 c. grated cheddar.
Spread into a baking pan (oiled/sprayed), dust with paprika, and bake until browned (about 40 minutes).
I like to serve it with a little feta and a sprinkling of sunflower seeds, and a dash of sriracha.