Place chicken breasts in large pot with salt & pepper. Cover with water and boil until done, about 45 minutes. Remove chicken and shred. Reserve 1/2 C of broth to use in place of water for the seasoning mix. Heat large skillet over med-high. Add chopped onion, chicken, 1/2 C chicken broth, and package of seasoning. Cook ingredients together, about 5-10 minutes, then add can of refried beans. Stir all ingredients together. Heat tortillas in microwave according to package directions. Spoon 1/8 of mixture in center of a tortilla, sprinkle with a little bit of cheese, fold and place in greased 9x13. Repeat process for remaining 7 tortillas. Cover top of burritos with remaining cheese. Bake in preheated 350 degree oven for 20-30 minutes. Serve with homemade Pico de Gallo (optional).