Set a deep 12-inch skillet with a lid over medium heat so it is ready when the chicken is seasoned.

Pat the chicken thighs dry with paper towels. Season both sides with 1 teaspoon of the salt and 1/2 teaspoon of the black pepper.

Add 1 tablespoon of the olive oil to the skillet. When the oil looks loose and shiny, put the chicken into the skillet in a single layer.

Cook the chicken for 4 to 5 minutes without moving it much, until the bottom is browned in spots and releases easily from the skillet.

Turn the chicken over in the skillet. Cook the second side for 2 to 3 minutes, until it has some color but the chicken is not fully cooked through yet.

Transfer the chicken from the skillet to a plate. Leave any browned bits and drippings in the skillet because they flavor the rice.

Add the remaining 1 tablespoon olive oil to the same skillet. Add the sliced mushrooms and spread them into an even layer.

Cook the mushrooms for 5 to 6 minutes over medium heat, stirring once or twice, until they give off their liquid and then start to brown around the edges.

Add the chopped onion to the skillet with the mushrooms. Sprinkle in the remaining 1/2 teaspoon salt and cook for 3 to 4 minutes, stirring often, until the onion softens.

Add the minced garlic to the skillet. Stir for 30 seconds, just until it smells fragrant.

Add the uncooked rice to the skillet. Stir for 1 minute so the grains are coated in the oil and mixed through the mushrooms and onion.

Pour the chicken broth into the skillet. Add the Dijon mustard and the remaining 1/4 teaspoon black pepper.