Heat the olive oil in saucepan over medium heat until hot.
Place the chopped red onion, cocoa powder, oregano, cumin, and garlic and cook over low heat until the onion is tender, stirring occasionally.
Stir in the diced tomatoes, paprika, chili powder and salt and bring to a boil.
Reduce heat to low, cover, and simmer for about 10 minutes. Remove from heat.
Mix the half of the sauce with the shredded chicken and 1/2 cup of grated cheese.
Preheat the oven to 350 degrees.
Put some olive oil on the bottom of a casserole pan.
Take a tortilla, cover 2/3 of it with the chicken mixture, then roll up the tortilla and place seam-side down in the casserole pan. Continue until all tortillas have been filled, rolled and placed in pan.
Add sauce to the top of the tortillas and cover with the rest of the grated cheese.
Cover the casserole with foil. Bake for about 20 minutes or until the cheese is melted and bubbly.
Garnish with cilantro leaves and serve.