In a large dutch oven or sauce pan, heat the oil over medium heat. Add in the chicken and cook to brown on both sides, about 5 minutes.
Add in the onion and celery and cook about 8 minutes to slightly brown on the edges.
Add in the garlic and mushrooms and cook about 5 minutes. Add in the coconut milk and chicken stock and scrape the bottom of the pan to incorporate any browned bits stuck to the pan into the sauce. Cover and bring to a light simmer. Cook about 15 minutes.
Remove the chicken from the pan and chop/shred it up. Return it to the pan. Add in the green beans. Simmer about 10 minutes.
Preheat oven to 400.
Pour the stew mixture into a baking dish. The broth itself will be thin, but there should be mostly solid pieces coming up just as high as the broth. If the solids are higher than the broth, you can add a little more chicken stock. If the solids sink too far into the broth, you can set a little of the broth aside.
Top the dish with tater tots so they completely cover the stew.
Bake for about 20 minutes until the top of the tots are browned.
Allow to cool for 10 minutes before serving.