Heat 1 1/2 cups broth and butter to boiling in a sauce pan. Add couscous and remove from heat. Stir well then cover and allow to set for 15-20 minutes. Heat extra virgin olive oil in skillet. Salt and pepper chicken tenders then brown in skillet for 5 minutes each side. In the meantime, cut the tender parts (white and light green) of the leeks lengthwise, then into slices. Rinse well. Add to the chicken and allow to wilt for 5 minutes. Add last 1 cup of chicken broth and let the liquid cook down at least 5 minutes. Fluff couscous with a fork and serve with chicken and leaks.