Heat olive oil in a large deep skillet or Dutch oven over medium-high heat.
Season the chicken pieces with salt and black pepper.
Add the chicken to the skillet and cook for 5-6 minutes until browned and cooked through, stirring occasionally. Remove the chicken from the skillet and set aside.
Reduce heat to medium and add the minced garlic to the same skillet. Cook for 1 minute until fragrant, stirring constantly to avoid burning.
Pour in the chicken broth and whole milk, stirring to combine.
Add the broken fettuccine pasta to the skillet, making sure the pasta is submerged in the liquid.
Sprinkle in the dried Italian seasoning and crushed red pepper flakes.
Bring the mixture to a boil, then reduce heat to medium-low and simmer uncovered for 12-15 minutes, stirring occasionally, until the pasta is tender and most of the liquid is absorbed.
Return the cooked chicken to the skillet and stir to combine.
Add the butter and grated Parmesan cheese, stirring until the cheese and butter have melted and created a creamy sauce.
Taste and adjust seasoning with additional salt and pepper if needed.
Remove from heat and sprinkle with chopped fresh parsley before serving.