Finely chop the onion into 1/4-inch pieces, chop the green bell pepper, dice the celery, and mince the garlic cloves. Slice the andouille sausage into 1/2-inch rounds. Shred the cooked chicken into bite-size pieces if not already done. Thinly slice the green onions on a diagonal and chop the fresh parsley. Having everything prepped and ready makes the cooking process smooth and ensures nothing burns while you're chopping.

Melt the butter in a large skillet over medium-high heat. Add the chopped onion and bell pepper, cooking for 3-5 minutes until they begin to soften and the onion turns translucent. Add the minced garlic and cook for about 1 minute until fragrant. Stir in the sliced andouille sausage and brown it for 3-4 minutes, breaking it up slightly as it cooks—this builds deep flavor that will infuse the entire dish. I find that browning the sausage first develops its smoky character much better than adding it raw to the rice cooker.

Transfer the sautéed mixture from Step 2 to your rice cooker. Add the long-grain white rice, chicken broth, shredded chicken from Step 1, diced celery, cajun seasoning, black pepper, and Worcestershire sauce. Stir everything together thoroughly to distribute the seasonings and ingredients evenly throughout the rice. Make sure the rice is submerged in the liquid for even cooking.

Close the rice cooker lid and press the cook button. Allow the rice to cook according to your rice cooker's instructions, typically 15-20 minutes. The rice cooker will automatically switch to warm mode when the rice is done. Let it rest on warm mode for about 5 minutes to allow the flavors to meld and any excess steam to escape.

Carefully open the rice cooker and fluff the jambalaya with a fork to separate the grains and distribute ingredients evenly. Stir in the sliced green onions and chopped parsley from Step 1 just before serving—adding them at the end keeps their fresh color and bright flavor from being lost to the heat. Serve directly from the rice cooker into bowls or plates.