Put the rice in a fine-mesh sieve and rinse it under cold running water, swishing the rice with your hand until the water runs clear. Transfer the rice to a medium bowl and add water to cover. Pour off any black bits or floating kernels, pour the rice back into the sieve to drain, then put it in a small saucepan. Add 1 1/4 cups water, a pinch of salt and the bay leaf; bring to a simmer. Cover the pan and reduce the heat to low. Cook 25 minutes, or until the rice is tender and the water has evaporated. (If liquid remains after the rice is done, drain it in a sieve.)
Meanwhile, preheat the oven to 375 degrees F. Heat the butter in a large high-sided skillet over medium heat. Add the leeks and celery and season with 1/4 teaspoon each salt and pepper. Cook until tender, about 10 minutes.
Add the flour to the vegetables and stir until well combined. Pour in the milk and bring to a simmer, whisking to prevent any lumps. Add the cream, chicken stock, thyme, nutmeg and 1/2 teaspoon each salt and pepper. Simmer over low heat until the floury taste dissipates, about 5 minutes.
Add the cooked chicken, wild rice (minus the bay leaf) and half of the cheese and heat until the cheese melts.
Put the crushed crackers in a heavy plastic bag and add 1/4 teaspoon pepper and the olive oil. Shake to combine and set aside.
Rub a 9-by-13-inch baking dish with a thin layer of soft butter. Pour the chicken mixture into the dish and top with the remaining cheese. Bake 25 minutes.
Pull the dish from the oven, sprinkle the cracker mixture over the top and bake until the crackers turn golden brown and the mixture bubbles in the center, 15 to 20 more minutes. Serve immediately.
Photograph by Christina Holmes
Recipe courtesy Amy Thielen for Food Network Magazine