Toss chicken with olive oil, blackened seasoning, salt, and pepper.
Heat skillet over medium-high heat and add olive oil. Add chicken and cook undisturbed for 4 minutes. Flip and cook another 2 minutes.
Reduce heat to low, add butter and garlic, and toss to coat. Cook until chicken reaches 165°F. Remove and set aside.
In the same pan over medium heat, add butter, shallot and chiles. Cook until softened.
Add garlic and cook 30 seconds until fragrant.
Pour in white wine and simmer 2–3 minutes, scraping the pan.
Add in chicken stock, spinach, linguine, Italian seasoning, salt, and pepper.
Bring to a gentle boil, then cover and reduce to low heat. Cook 15–20 minutes until pasta is tender.
Stir in heavy cream and simmer gently.
Add parmesan and stir until melted.
Stir in lemon zest and juice.
Return chicken to the pan and toss to combine. Let it simmer to a gentle boil for another 2–3 minutes until warmed through and sauce thickens.