Heat olive oil in a large pan, add chicken, season with salt and pepper and cook til no longer pink.
Remove chicken from pan and set aside.
Add onions and garlic, season with salt and saute at medium high til onions are soft and garlic is fragrant
Add milk and parmesan, stir to melt in the parmesan and bring to a simmer
Add pepper slices and cook 2-3 minutes. Then stir in parsley.
Remove from heat and blend everything in the pan with an emulsion blender in the pan. Or pour into a food processor and process smooth and return to pan.
Return chicken back to the pan and simmer sauce another 3-4 minutes for it to thicken up. Add drained, cooked pasta to sauce, toss to combine, serve with parmesan and fresh parsley