Heat olive oil in a large pot over medium heat. Add diced onion, carrots, and celery. Cook for 5–7 minutes until softened. Stir in garlic and cook for another minute.

Add the chicken thighs or breasts directly to the pot. Pour in chicken broth and add thyme, rosemary, bay leaf, salt, and pepper. Bring to a boil, then reduce heat and simmer for 25–30 minutes, until chicken is cooked through and tender.

Remove the chicken and shred it with two forks. Discard the bay leaf, then return the shredded chicken to the pot along with the potatoes. Simmer for another 10–12 minutes, until potatoes are fork-tender.

In a small pan, melt butter and whisk in flour to make a roux. Cook for 1–2 minutes, then stir this mixture into the stew. Continue simmering for 5 minutes, stirring until thickened.

Stir in the peas and cook for 2–3 more minutes until heated through. Taste and adjust seasoning as needed. Serve hot, garnished with chopped parsley if desired.