Stewing the chicken on the bone makes it tender and juicy.
Season chicken breasts with salt and pepper. Heat olive oil in a large skillet, add chicken, and cook over medium-high heat until golden brown on both sides, about 7 minutes total.
Add stock and tomatoes, bring to a boil, and cover. Cook on medium-low heat for about 20 minutes; remove chicken, and set aside.
Add carrots to skillet, and cook, covered, until almost tender, about 5 minutes. Add asparagus, leeks, and peas, and cook until all the vegetables are tender, about 5 more minutes.
Meanwhile, pull chicken from bone, and shred into large bite-size pieces. Return chicken to skillet, and cook until heated through, about 2 minutes. Garnish with sprigs of parsley, if desired.