In a large pot or Dutch oven over medium-high heat, cook the bacon until crispy. Add chicken and season with salt, pepper, and garlic powder. Cook until the chicken is no longer pink, then remove from the pot and set aside.
Add the onions and garlic and cook to the pot and cook until softened. When onions are caramelized, add spinach and cook until wilted. Add the milk and bring to boil. Add the fettuccine to the boiling milk and cover. Cook the fettuccine over medium heat until the milk thickens and the pasta is cooked, about 7 minutes.
Return the chicken to the pot. Stir in the pesto and Parmesan. Garnish with parsley and more Parmesan.