Prep the vegetables: Chop onion, carrots, celery, and potatoes. Trim the green beans. Keep peas in the freezer for now.
Season the chicken: Pat the chicken dry and season with 1 teaspoon salt, pepper, and smoked paprika.
Cut into large chunks if you prefer, or leave whole to shred later.
Layer into the slow cooker: Add onion, carrots, celery, potatoes, green beans, garlic, thyme, rosemary, bay leaf, and diced tomatoes (if using). Nestle the chicken on top.
Whisk the broth: In a bowl, whisk chicken broth with tomato paste until smooth. Pour over everything in the slow cooker.
Cook low and slow: Cover and cook on Low for 6–7 hours or on High for 3.5–4 hours, until the chicken is tender and the vegetables are soft.
Shred or cube the chicken: Remove the chicken and shred with two forks, or chop into bite-size pieces.
Return it to the pot.
Add peas and finish: Stir in frozen peas. Cover and cook on High for 10–15 minutes more to heat through.
Thicken if desired: For a heartier texture, mix cornstarch with cold water to make a slurry. Stir into the stew and cook on High for 10–15 minutes until slightly thickened.
Season to taste: Taste and adjust salt, pepper, and acidity.
A small squeeze of lemon can brighten the flavor.
Serve: Ladle into bowls and garnish with chopped parsley and a drizzle of olive oil if you like.