Cook pasta "al-dente" according to package directions. Drain and set aside. (try to time so pasta is finished when sauce is finished).
Cube or shred chicken and set aside.
Prepare Alfredo Sauce:
In large cast iron skillet (or any oven proof skillet), over med/high heat cook bacon until crispy. Remove and set aside. If needed drain excess grease from pan (a little is ok).
Reduce heat to medium, add olive oil and chopped onion, cooking 2-3 minutes. Add garlic and cook until onion is translucent and tender.
Add flour to pan, stir to combine with onion mixture and cook for 1-2 minutes.
Add chicken broth and whisk until smooth.
Add in milk and again whisk until smooth. Cook, whisking regularly until sauce begins to thicken.
Stir in parmesan cheese, salt and pepper.
Gently add in cooked pasta and cubed chicken, lightly stirring to combine. Top with grated jack cheese, 1/2 cup parmesan cheese, and bacon crumbles.
Cook in preheated 375* oven for 20-30 minutes or until bubbly hot, golden, and the edges just begin to crisp.