Step 1

Pull the skin off the chicken thighs and set aside if you intend to render fat from it for this braise. Cut each bone-in thigh into two pieces. Transfer the cut thigh pieces to a bowl and season with 2 teaspoons of fish sauce and the black pepper. Set aside to marinate for 10 minutes.

Step 2

Set a medium Dutch oven over medium-high heat. Add the chicken skin and after things sizzle, cook for 5 to 8 minutes, stirring often to render the fat from the skin. When you have 3 to 4 tablespoons of the fat rendered, use a slotted spoon to transfer the skin to a plate, leaving the golden fat behind. (If you do not want to use a skin, combine the olive oil and butter in the pan; use the same heat and heat until the butter starts to foam.)

Step 3

In two batches, sear the marinated chicken in the pot for about 1 minute, stirring often, until the exterior no longer looks raw. Hold the seared chicken on a plate (or return it to the bowl) as you work.

Step 4

After searing the chicken, add the onions to the pot. Cook, stirring for 8 to 10 minutes until there are many brown pieces. Add the garlic, if using, during the last 1 minute to aromatize. Make sure to stir the bottom of the pot to lift off any bits stuck there.

Step 5

Add the tomato paste and cook for 30 to 60 seconds, stirring constantly, to prevent scorching. Return the seared chicken to the pot, stir well to coat the chicken with the tomato onion mixture, and splash in a bit of water to prevent scorching and scrape the bottom and sides of the pan. Turn down the heat to low, cover, and let cook gently for 10 minutes.

Step 6

Remove the lid, add the potatoes, carrots and bay leaf. Pour in the chicken broth and if needed, water to cover about 80 percent of the chicken and vegetables. Increase the heat to bring to a boil, then turn down the heat to gently simmer. Cover and cook until the potatoes are easily pierced with the tip of a knife 5 to 10 minutes.

Step 7

Add the mushrooms, stir, and keep simmering, uncovered, until the mushrooms are cooked and tender, 5 to 8 minutes. Turn off the heat, taste the broth, and add up to 2 tablespoons fish sauce to inject a salty umami flavor. Remove the bay leaf and serve the ragout in shallow bowls. Crumble on the crispy chicken skin, if you like! Sop it up with lots of bread or present with rice or noodles.