Devein and dry roast the ancho chiles on a comal overn an open fire or in a cast-iron pan over medium-high heat until they begin to blacken and blister. Place the toasted chiles in a spice grinder and process to a fine powder.
Dry roast the onion and garlic on a comal over an open fire or in a cast-iron pan over medium-high heat until they begin to blacken and blister. Transfer the piloncillo, pulque, agave, tequila and chile powder to a blender and process until smooth. Heat the lard and fry the chile mixture. Season with salt and cool. Marinate the short ribs overnight in the chile mixture.
The next day, preheat the oven to 375 degrees F. Dry roast the agave leaves on a comal over an open fire or in a cast-iron pan over medium-high heat. Arrange the leaves in the bottom of the pan, to act as a steamer. Place the ribs on top of the leaves and cover with the marinade. Cover with the cactus paddles and seal with foil or a tight-fitting lid. Transfer to the oven and cook for about 4 hours.
Slice the cactus paddles into strips and divide the cactus and short ribs among 4 serving dishes. Serve with beans and tortillas.