Butterfly the chicken breast into two even cutlets if using a large breast, or pat thin breasts to an even thickness. In a bowl, whisk together eggs and whole milk until smooth.
Dip the chicken into the egg wash, allowing excess to drip off, then coat thoroughly in the crispy chicken coating, pressing firmly to ensure full coverage. Let the coated chicken rest for 5 minutes to help the breading adhere.
Heat vegetable oil in a deep skillet to 350°F, using enough oil to come halfway up the chicken. Fry for about 5 minutes per side until golden brown and the internal temperature reaches 165°F, then transfer to a wire rack.
In a saucepan over medium heat, cook pancetta in olive oil until crispy and rendered, about 4–5 minutes. Add minced garlic and red pepper flakes, stirring for 30 seconds until fragrant.
Stir in crushed tomatoes, salt, black pepper, and sugar, then simmer for 10–15 minutes until slightly thickened and rich. Spoon marinara over the fried chicken, then top evenly with mozzarella and grated Parmesan.
Broil on high for 2–3 minutes until the cheese is melted, bubbly, and lightly golden. Garnish with fresh basil and serve immediately while hot and crispy.