Preheat the oven to 200C (400F).
Rub the chicken with 2 tablespoons of olive oil, thyme, salt, and pepper.
Place the chicken in a roasting pan and cook for 50 minutes or until the internal temperature reaches 75C (165F).
While the chicken is roasting, rinse the lentils under cold water and place them in a saucepan with the chicken stock and bay leaf.
Bring the lentils to a boil, then reduce heat and simmer for 20 to 25 minutes until tender but firm. Drain any excess liquid and discard the bay leaf.
In a small bowl, whisk together the extra virgin olive oil, Dijon mustard, lemon juice, and minced garlic to create the dressing.
Remove the chicken from the oven and let it rest for 10 minutes before carving or shredding the meat into bite-sized pieces.
In a large mixing bowl, combine the warm lentils, diced red onion, baby spinach, and the dressing. Toss until the spinach is slightly wilted.
Divide the lentil mixture among plates and top with the roasted chicken portions.