Keeping the same pan over medium heat, add the peppers and prosciutto and cook until the peppers have browned and the prosciutto is crisp, about 5 minutes. Add the garlic and cook for 1 minute. Add the tomatoes, wine, and herbs. Using a wooden spoon, scrape the browned bits off the bottom of the pan. Return the chicken to the pan, add the stock, and bring the mixture to a boil. Reduce the heat and simmer, covered, until the chicken is cooked through, about 20 to 30 minutes.
If serving immediately, add the capers and the parsley. Stir to combine and serve. If making ahead of time, transfer the chicken and sauce to a storage container, cool, and refrigerate. The next day, reheat the chicken to a simmer over medium heat. Stir in the capers and the parsley and serve.