Put the salt on a cutting board along with the garlic cloves, mince and mash the garlic into the salt, to make a paste. Stir in the cayenne. Rub the mixture onto the chicken pieces, making sure each is evenly covered. Let sit in a bowl at room temperature for 30 minutes.

Heat oil in dutch oven until very hot. Add the chicken pieces and cook until meat is done, 5–8 minutes per side. Remove chicken from oil and let drain on paper towels. Heat the stock in a separate pan, and leave it simmering on a back burner.

Stir oil in pan to loosen any stuck particles, then return to high heat. Using a long-handled metal whisk, gradually stir in the flour. Cook, whisking constantly, until roux is dark red-brown to black, being careful not to let it scorch or splash on your skin. This will take several minutes. Remove from heat and immediately add the vegetables, stirring constantly until roux stops getting darker. Return pan to low heat and cook until vegetables begin to soften, about 5 minutes, stirring constantly and scraping the pan-bottom well.

Add the hot stock to the roux by ladle-fuls, stirring until well mixed after each addition. Return to a boil, scraping and stirring. Add the andouille and garlic, and simmer 45 minutes, stirring occasionally.

Strip the collard green leaves from the ribs, and discard the ribs. Gather the leaves into a stack and cut them into strips that are a half-inch wide by 2–3 inches long. Cube the chicken.

Add the chicken and greens to the gumbo, season to taste, and cook for a few minutes until the greens are cooked. Serve with rice.