Traditionally made with nopales (edible cactus) which gives the dish a distinctive flavor. Look out for them in specialty stores. For this recipe you need a 12-14 oz can of nopales or fresh, peeled, blanched, sliced nopales.
NOTE: to reconstitute dried chipotle chilies place the chilies in a pan with enough water to cover. Protecting your face against fumes and making sure the kitchen in well ventilated, bring the chilies and water to a boil. Cook for about 5 minutes then remove from heat. Cover and let stand until softened.
Place the flour in a large bowl and season with salt and pepper. Add the beef and toss to coat well. Remove from the bowl, shaking off the excess flour.
Heat the oil in a skillet and brown the meat briefly over a high heat. Reduce the heat to medium, add the onions and garlic and cook for a further 2 minutes.
Add the tomatoes, chilies, and stock. Cover and simmer over a low heat for 1 1/2 hours or until the meat is very tender. Top and tail the green beans and add them to the pan 15 minutes before the end of cooktime or until the way your like them. Skim off any fat that rises to the surface.
Transfer to individual bowl and serve with beans and rice.