Heat bacon in a large Dutch oven over medium heat. Cook, flipping occasionally until browned and crisp, about 10 minutes. Drain on paper towels.
Sprinkle chicken evenly with salt and pepper; cook in hot bacon drippings over medium-high heat, stirring often, until chicken is golden brown on all sides, about 4 minutes. Transfer chicken to a plate and set aside. Chicken will not be fully cooked at this point.
Add shallot and garlic to drippings and cook, stirring often, until fragrant, 2 minutes. Stir in water and milk; use a wooden spoon to scrape any browned bits from bottom of the Dutch oven. Stir in pasta and ranch dressing mix. Bring to a boil and simmer for 6 minutes.
Return chicken to the Dutch oven and add broccoli. Cook until pasta is tender and chicken is cooked through, 3 to 4 minutes. Stir in Cheddar cheese and sour cream to combine. Crumble cooked bacon over the top and serve hot.