Step 1Remove the tough stems from the greens and wash the leaves well in several changes of cold water. Place them in a large pot and add the hot pepper flakes and 1 teaspoon salt. Add water to cover by several inches and bring to a boil. Reduce the heat to a simmer and cook, uncovered, until the greens are very tender, about 1 hour. Drain well and cool slightly, then squeeze dry and finely chop.
Step 2While the collards are cooking, melt the butter in a large saute pan over medium heat. Add the onion and garlic, sprinkle lightly with one-fourth teaspoon salt and cook, stirring, for 5 minutes. Add the shiitakes and the tamari and saute until they are tender, about 10 minutes. Remove from the heat and cool slightly.
Step 3Heat the oven to 350 degrees. Butter a 9-by-13-inch baking dish.
Step 4Combine the collards and shiitakes in a bowl. Add the eggs, cheese and bread crumbs and mix well. Spread into the prepared pan. Bake 30 minutes. Cut into squares to serve hot or at room temperature.