Place chicken in a saucepan and cover with water by 2 inches. Add bay leaf and a healthy pinch of salt. Bring to a boil and then reduce to a simmer until chicken is cooked through. Remove the chicken, reserving the cooking liquid, and let cool slightly. Shred the chicken with 2 forks and set aside.

Heat oil in a large, non-stick skillet over medium-high heat. onion and garlic and sauté for a few minutes, until soft. Add tomato paste, cumin, smoked paprika, coriander, and shredded chicken and stir. Season to taste with salt and pepper. Add the juice of half of the lime. If the chicken is dry, add a few tablespoons of the reserved cooking liquid (I ended up adding 3 tablespoons). Stir to combine and heat through.

To serve, place chicken on a double layer of warmed tortillas. Top with avocado, cilantro, tomatoes and radishes. Squeeze a lime wedge over each taco before digging in, if desired.