Begin by finely chopping the onion, green bell pepper, red bell pepper, celery, and garlic. Set aside all the chopped vegetables in separate bowls.

In a large skillet, heat a tablespoon of avocado oil over medium-high heat. Season the boneless chicken thighs with Cajun seasoning and sear them for about 3-5 minutes per side until golden brown. Remove and set aside.

Reduce the heat to medium-low, add the unsalted butter to the skillet, and whisk in the all-purpose flour. Stir constantly for about 10-15 minutes until the roux is medium brown.

Add the chopped onion, green bell pepper, red bell pepper, celery, and half of the green onions to the roux. Sauté for approximately 8-10 minutes, then incorporate the minced garlic and cook for another minute.

Gradually whisk in the warmed chicken broth until smooth. If using, add browning sauce now. Return the seared chicken thighs to the skillet, cover, and simmer on low for about 30 minutes.

After simmering, remove the chicken, cut it into bite-sized pieces, and return to the pot. Stir in chopped parsley and adjust seasoning if necessary.

Serve the Chicken Étouffée over warm cooked white rice, garnished with the remaining green onions.