The evening before you plan to cook dinner, salt the boneless, skinless chicken thighs with Kosher salt.
Arrange the salted chicken thighs on a wire rack on an aluminum-foil-lined sheet tray, and store the chicken in the fridge for 12-24 hours.
*Resting the salted chicken in the fridge overnight will give the salt time to penetrate the meat. The aluminum foil is just there to catch any liquids and to make cleaning your sheet tray easier.
The following day, when you are ready to start cooking your chicken and preparing dinner, separate the parsley leaves from the stems, and store the parsley leaves in a piece of paper towel in a covered container in the fridge.
Add the parsley stems to the chicken stock, and bring the stock to a very low simmer in a stock pot or Dutch oven on the stove.
Cut the chicken into large, bite-sized pieces.
Add the chopped chicken to the hot chicken stock, and wait for the mixture to reach a low simmer again.
Reduce the heat to the lowest setting on your stove, and allow the chicken to braise for roughly two hours, or until the chicken is completely fork tender and nearly falling apart when you try to remove it from the liquid.
While the chicken is cooking, prepare the velouté-style gravy.
For the gravy, melt 5 Tablespoons of butter in a medium-sized soup pot on the stove.
When the butter is melted, add the 5 Tablespoons of all-purpose flour.
Stir with a rubber spatula while the butter and flour (roux) mixture cooks over medium heat for roughly 6-7 minutes.
Slowly whisk in the whole milk, adding small amounts in stages.
When the milk is fully incorporated with the butter and flour mixture, whisk in some of the hot chicken stock from your chicken braise until your sauce reaches your desired consistency.
*I aim for a consistency in the sauce similar to Thanksgiving gravy. Thick, but not too thick.
Taste the sauce, and add Kosher salt and freshly-ground black pepper.
Remove the chicken from the stock, and set the braised chicken thighs aside for later.
*Save the chicken stock to cook your rice.
Rinse the long-grained rice under cold water, and drain.
Add the drained rice to a rice-cooking pot with 1.5 cups of the chicken stock that you used to cook the chicken earlier.
Add ½ teaspoon of Kosher salt to the liquid, and increase the heat to high.
When the liquid in the rice pot is starting to simmer, cover tightly with a lid or aluminum foil, and reduce the heat to the lowest possible setting.
Cook the rice covered for 15 minutes.
While the rice is cooking, finely chop the parsley leaves that you separated from the stems earlier.
When the rice has cooked for 15 minutes, remove the lid, and add ½ of the chopped parsley leaves.
Fluff the rice gently with a fork to distribute the parsley among the grains of cooked rice, and cover again with a lid.
Mix the remaining fresh parsley into the gravy that you prepared earlier.
Add the cooked chicken to the gravy mixture, and stir to coat the chicken in the sauce.
Prepare warm serving bowls with a large scoop of herb rice in the bottom of each bowl.
Top with the chicken and gravy and parsley mixture.
Serve hot.