1 cup prepared chili
1/2 cup shredded cheddar cheese
4 boneless, skinless chicken breasts (about 2 pounds total)
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Arrange a rack in the middle of the oven and heat to 400°F. Line a rimmed baking sheet with aluminum foil or parchment paper.
Stir together the chili and cheese in a small bowl.
Use a paper towel to pat the chicken breasts completely dry and place on a cutting board. Using a sharp knife and keeping it parallel to the cutting board, make a deep slit into the meatiest side of each breast, cutting far enough to create a pocket. Be sure not to slice all the way through the chicken breast.
Divide the chili and cheese mixture among the pockets. Stick 2 or 3 toothpicks through the open end of each chicken breast to keep the filling from spilling out.
Transfer the chicken breasts to the prepared baking sheet. Brush the tops of the chicken with oil, then season with salt and pepper. Bake until lightly browned and the internal temperature registers 165°F, 25 to 30 minutes. Let the chicken rest for about 5 minutes. Remove the toothpicks and serve.