In a medium- large skillet, add oil, onions, garlic, tomatoes and chipotle sauce. Sauté, for about 2-3 minutes, stirring constantly to prevent any burns. Then add chicken or pork, taco seasoning, cumin, cilantro and ½ cup chicken broth or water bring to a boil and let it simmer for all the flavors to come together about 8-10 minutes, stirring occasionally. Until all the liquid has evaporated. Remove from the heat.
Oil baking sheet with a generous amount cooking spray or brush with butter. Place about 1/3 to ½ cup of the chicken mixture in the center of each tortilla leaving a 2-inch border on both ends. Top with beans, cheese, and cilantro. Fold in the ends and roll up.
Place the chimichangas seam-side down on the baking sheet; brush with the butter or oil. Bake 8 to 10 minutes per side, brushing again after you flip with spatula, until golden brown Garnish with desired toppings and serve with guacamole.