Warm 1 tablespoon oil in a large, wide pot over medium heat. Add 1 diced onion, 10 grated garlic cloves, and a 2-inch piece of ginger, grated to the pot and cook until translucent and tender, about 4 minutes. Stir in 2 cups white rice for 1 minute. Stir in 1 cup coconut milk (if there’s a hard layer on top of the can, scoop half of it into the pot and keep the other half in the can), 2 1/2 cups water, 1 tablespoon sugar, and 1 teaspoon kosher salt.
Season 2 pounds of chicken thighs generously with salt and pepper and lay the chicken thighs over the rice. Overlap them slightly if needed to fit all of the chicken into the pot.
Bring the liquid to a simmer, then reduce to low heat and cover the pot. Cook for 20 to 25 minutes, until the rice is tender and the chicken is cooked through. Remove pot from heat and leave covered for an additional 10 minutes to allow the rice to steam.
While the chicken and rice are cooking, make the Peanut Coconut Curry Sauce.
Warm 1 tablespoon olive oil in a small pot over medium heat. Stir in 1 tablespoon red curry paste until very fragrant and beginning to stick to the bottom of the pot, about 1 minute. Stir in 1/2 can (the remaining) coconut milk, 1 heaping tablespoon of peanut butter, 1 tablespoon soy sauce and 2 teaspoons fish sauce. Simmer until very thick, like heavy cream or a thin yogurt, about 5 minutes. Remove from heat and allow to cool.
Scatter 1/4 cup chopped cilantro and 3 sliced scallions over top of the chicken and rice. Serve with peanut sauce.