Step 1

Finely dice 1 small shallot and mince 6 garlic cloves. Finely grate 1 ounce Parmesan cheese (about 1/2 packed cup). Pick the leaves from a few freshly parsley sprigs and finely chop until you have 2 tablespoons.

Step 2

Place 1 of the boneless, skinless chicken breasts inside a gallon zip-top bag. Use the flat side of a meat mallet or a rolling pin and pound until 1/2-inch thick. Repeat with the remaining 3 chicken breasts. Pat the chicken dry with paper towels and season all over with 1 teaspoon of the kosher salt and 1/4 teaspoon black pepper.

Step 3

Heat 2 tablespoons olive oil in a 10-inch or larger skillet over medium-high heat until shimmering. Add 2 of the chicken breasts and sear until deeply browned, 5 to 7 minutes per side. Transfer to a plate. Repeat with the remaining chicken.

Step 4

Reduce the heat to medium and melt 2 tablespoons unsalted butter in the skillet. Add the shallot and garlic and cook until fragrant, about 30 seconds.

Step 5

Add 1 cup half-and-half or whole milk, 1/2 cup low-sodium chicken broth, and the remaining 1/2 teaspoon kosher salt. Bring to a boil over high heat. Reduce the heat to a maintain simmer. Add the Parmesan and stir to combine. Return the chicken and any accumulated juices to the pan. Simmer until the sauce is slightly thickened and the chicken is cooked through, 2 to 3 minutes. Garnish with the parsley before serving.