In a crockpot add the diced tomatoes and marinara sauce. Combine the evaporated milk and cornstarch and pour in the crockpot. Add the minced garlic, dried thyme, salt and pepper.
Add the chicken. Cover the chicken with the sauce. Season again with salt, pepper, and Italian seasoning.
Cook on low for 6-8 hours. Once done, chunk up or shred the chicken. Serve over pasta.