*Use between 7 and 11 of the above greens.
Fill a large stockpot with water and bring to a boil.
Wash all greens thoroughly in salted water, making sure to remove any grit, discolored outer leaves, and tough stems. Rinse greens in a bath of unsalted water (a clean double sink works well for this). Drain greens briefly in a colander.
Place half the greens, half the onions, and half the garlic in the stockpot. Bring back to a boil over high heat; reduce heat to a simmer and cook for about 20 minutes, until greens are very tender. Using a slotted spoon, transfer them to a large bowl to cool. Repeat the process with the second half of the greens, onions, and garlic, cooking them in the same water. If half of the greens overfills your pot, you may cook them in three batches, still using the same cooking water. When all greens have finished cooking, reserve cooking liquid.
While greens are cooking, make a roux by heating vegetable oil to almost smoking in a heavy skillet. Whisk or stir in flour, moving quickly to avoid burning. Continue to whisk or stir constantly until roux reaches a dark peanut butter color. This should take about 10 minutes, depending on the temperature of your burner. If you fear burning the roux, cook it more slowly at a lower temperature. Set roux aside briefly.
In batches, process greens, onion, and garlic in a food processor or meat grinder until completely puréed. Use a little cooking liquid to loosen them while puréeing if necessary.
If you have a very big stockpot, you may finish the gumbo in just one pot. Otherwise, use two pots. Pour puréed greens into stockpot(s), adding cooking liquid until you have a mediumthick soup. Bring to a simmer over medium-high heat and slowly stir in the roux by large spoonfuls, making sure all roux incorporates. Add thyme, cayenne pepper, and bay leaves.
Continue to simmer gumbo for about an hour, or until all flavors have merged. Stir often to avoid burning. If at any point the gumbo appears too thick, add more of the greens cooking liquid. Add salt to taste. Five minutes before cooking is complete, stir in the red beans.
If desired, slowly add the filé at the end of cooking, taking care that it doesn’t get lumpy.
Serve gumbo over rice.