For the green seasoning: Put the cilantro, celery, chile, onions, oil, ginger, thyme leaves and garlic cloves in a blender. Process until a paste forms.
For the marinade and chicken: Add the onion, chile, curry powder and chicken to a large bowl. Add the green seasoning and toss to combine. Cover the bowl or transfer to a resealable bag and refrigerate for at least 24 hours.
Preheat the oven to 350 degrees F.
Heat the oil in a large Dutch oven over medium-high heat until smoking. Working in batches, remove the chicken from the marinade, scraping off the onions. Sear the chicken until it's brown on all sides, about 5 minutes per side. Keep the rest of the marinade. Remove the chicken to a plate and set aside.
Add the remaining marinade and a pinch of salt to the Dutch oven and cook, stirring occasionally and scraping up the brown bits that cling to the bottom, until the onions are softened and the brown bits on the bottom have been released, about 5 minutes. Add the chicken broth and the seared chicken, along with any juices, back to the pot. Cook for 35 minutes, stirring occasionally, then add the potatoes and cook until the chicken is tender and cooked through, the potatoes are tender and the liquid is reduced by half, 10 minutes more.
For the rice: While the chicken is cooking, melt the butter in a medium saucepan over medium-high heat. Add the rice, stir to coat, and toast until translucent about 2 minutes. Add 1 1/2 cups water and a pinch of salt. Bring to a boil, then cover and place the saucepan in the oven, until the water is fully absorbed, about 18 minutes. Remove the lid and fluff the rice with a fork, then cover until ready to serve.
Remove the Dutch oven from heat and add the lime juice and salt to taste. Serve the curry over the rice and garnish with the green onions.
Wear gloves while handling the Scotch bonnet chile and avoid touching your eyes.