Adapted from Rick Bayless. This is written to serve a crowd, for something like a Super Bowl watching party. It can easily be divided to serve less people, in which case use a smaller pan or baking dish.
Roast the poblano peppers on all sides. I prefer the broiler, but you can also hold them above a gas flame if you have a gas stove. When they are blackened on all sides, remove to a bowl and cover it with a towel.
Let the peppers rest for 5 minutes. Then peel the blackened skin off, remove the inner core with the seeds, and quickly rinse the remaining seeds out.
Chop the peppers and set aside.
Brown the chorizo over medium heat in a heavy bottomed pan. I prefer enameled cast iron if you have the right size, because it is gorgeous for then serving the dip as well. But stainless steel works too. Break it up and let it cook for 5 minutes.
Keep breaking and stirring the chorizo. Add the onions with a tiny pinch of salt.
Cook until completely browned and the onions have become translucent, about 10 minutes. If you are using an attractive enameled cast iron pan, turn the broiler onto high. If you are using a stainless steel pan, you should skip the browning of the top.
Add the chopped roasted poblanos. Stir and let everything heat up, about 1-2 minutes.
Add the cheese in 4 batches, slowly stirring it in and letting it melt. In between batches, add the cream in 3 batches. Add the hot sauce with the cream if using. Keep stirring the entire time.
When the cheese is completely melted and the dip has been stirred smooth, it is time for the broiler. If you are using an attractive enameled cast iron pan, place the pan under the broiler for a just a few minutes, just until the dip starts to brown in spots. If you are using a stainless steel pan, transfer the dip to a serving dish and proceed with serving directions below.
Sprinkle crumbled dried Mexican oregano over the bubbly queso fundido and serve immediately. If you can place the dish over a warmer, all the better--but this stuff is so delicious people will probably keep eating it cool!
When I first learned to make this, I used exclusively Oaxacan string cheese (similar to Mozzarella)--which necessitated a trip to the Mexican market. At my local grocery store here, however, they have Chihuahua cheese pre-shredded, as well as a mix of Chihuahua, Oaxacan string cheese and Cotija pre shredded. So I bought bags of each and used a mix. If you cannot find that, I recommend looking for Oaxacan string cheese, Chihuahua cheese and then a mix of Mozzarella and Monterey Jack--in that order!
The heavy cream is not traditional; I add it because traditionally queso fundido is eaten with warmed corn tortillas. The cream helps to loose the dip, so that it can be scooped by the more fragile tortilla chips. Because of this cream, you might prefer to add a little hot sauce. My kids loved it without the hot sauce, my husband practically required the hot sauce, and I was happy either way.