In a medium cast-iron skillet, cook the pancetta over medium heat until crispy. Remove the crispy pieces and leave the remaining fat in the skillet.
Place the cooked pancetta in a medium-sized bowl with the crème fraiche, shredded cheese, chopped basil, lemon zest, sun-dried tomatoes, salt and pepper, and mix to combine.
Using a paring knife, cut a 3-inch long pocket into the side of each chicken breast. Fill each with the cheese mixture and fold the chicken over to enclose.
In a shallow dish, add the flour, 1 teaspoon salt and 1/2 teaspoon pepper. Mix with a fork to combine. In a separate shallow dish, add the eggs and milk, and whisk to combine. Season with 1 teaspoon salt and 1/2 teaspoon of pepper. Place the breadcrumbs and Parmesan cheese in a third shallow dish.
Coat the chicken with the flour, carefully shaking off any excess. Next, dip into the egg mixture followed by the breadcrumb mixture and press to fully coat.
Place the chicken back into the cast-iron skillet with leftover pancetta fat, drizzle with olive oil and bake for 20 to 30 minutes, until golden brown and the internal temperature reaches 165 degrees. For extra browning, broil the chicken for 5 minutes before removing from the oven.