Sprinkle the diced chicken breast liberally with salt and pepper. Turn on the Sauté function at 320°F for 15 Minutes. Melt the butter in the pot. Brown the chicken on all sides, working in batches so as to not overcrowd the pot. Return all chicken back to the pot.
Add the minced onion and garlic and sauté until fragrant, about 5 additional minutes.
Add the chicken broth, diced sundried tomatoes, and penne pasta. Stir to evenly coat all noodles.
Place the lid on top and Slow Cook on High for 2 Hours, or on Low for 3 ½ -4 Hours.
After 30 Minutes of slow cooking on high, remove the lid and stir the pasta. Return the lid on the pot and continue cooking.
After 1 Hour, add the cream cheese, cheddar cheese, and parmesan cheese. Stir to combine. Place the lid on and continue cooking until time is over.
Once the pasta has cooked, mix in the oregano and cream. Fold in the spinach and keep warm until wilted. Serve immediately.