Saute onion in oil for about 3 minutes. Stir in the flour, salt, ground pepper, tarragon, chicken broth and milk and cook until the mixture thickens, stirring constantly.Advertisement
Add the chicken pieces to the mixture. Blend in the egg yolk, then the lemon juice, sherry and bell pepper. Cook until chicken is heated through, about 5 minutes. Stir in the avocado and serve on toast! Voila!