Heat the olive oil in a large 10” (28cm) Dutch oven with lid. Add the onions and allow them to brown over medium heat for a minute or two. Add the beef cubes and allow to brown well uncovered for about 5 minutes. Pour in the bottle of beer, add the minced garlic, cover, and allow to simmer over medium heat for one hour. Check occasionally to make sure the stew does not dry out. You can add a half cup (120ml) of water if you think the stew is too dry.

Meanwhile, roast the fresh Poblano or Anaheim chiles on an open gas flame on your stove, or under a heated electric broiler. (For more instructions, click here.) Once the chiles are blackened, remove from the heat, and wrap in a clean kitchen towel. Place the towel in a paper or plastic bag, and allow the chiles to sweat for about 20 minutes. Remove the chiles from the bag and towel, scrape away the loose, blackened skin, remove the top stem and seeds, and then rinse. Chop the chiles into strips, and then set aside.

Prepare the mashed potatoes by first boiling the prepared potatoes in salted water. Drain the water, add the butter and milk, and mash until smooth. Set aside until your guisado is ready.

When the meat of the guisado is fork tender, remove from the heat. Toss in the roasted chiles. Serve the guisado over the mashed potatoes, and garnish with thick slices of fresh avocado.