Tear the chiles into large pieces, then cook them in a dry skillet set over medium heat until lightly browned and very aromatic. Transfer them to a large bowl, cover with boiling water, and set aside for 20 minutes.
Meanwhile, melt 2 Tbs. of the bacon fat in a large Dutch or French oven over medium heat. Add the onion and garlic; cook, stirring often, until wilted, about 3 minutes.
Push the onion and garlic to the sides of the pot, then add the meat chunks in batches, browning them well in the residual fat. As they brown, transfer them to a plate and add more until all are nicely done.
Take the pot off the heat. Scoop out the onion and garlic and place them in a blender or in a food processor fitted with the chopping blade. Drain the chiles in a colander set in the sink, then add them to the blender or food processor. Also add the Worcestershire sauce, thyme, oregano, cloves, pepper, and bay leaf. Blend or puree until smooth.
Melt the remaining 2 Tbs. bacon fat in the pot set back over medium heat. Scrape the chile paste into it and fry for 3 minutes, stirring almost constantly.
Return the meat and any juices on the plate to the pot. Also add the broth and vinegar. Bring to a simmer, stirring occasionally; then cover, reduce the heat to very low, and cook, stirring occasionally, for 1 hour.
Add the plantains to the pot and continue cooking, stirring once in a while, until the meat is falling-apart tender, 1 to 1-1/2 additional hours.
Photo: Marcus Nilsson