Step 1Char the poblano over a gas flame or under the broiler until black and blistered on all sides. Cool, then slip off the skin and remove the seeds. Cut the flesh into medium dice and set aside.
Step 2Heat the oven to 350 degrees.
Step 3Peel and seed the pumpkin. Cut half the flesh into 1-inch cubes and half into one-half-inch cubes (the smaller cubes will soften to thicken the sauce). Heat 2 tablespoons of the olive oil in a large skillet over high heat. Add pumpkin cubes and add the salt. Cook, shaking pan or flipping pumpkin with a spatula, until edges start to caramelize, about 10 minutes. Remove with a slotted spoon to a Dutch oven or a deep casserole.
Step 4Quarter the shiitakes. Add 2 tablespoons of the oil to the skillet and heat briefly, then add the shiitakes. Reduce the heat to medium and cook, shaking the pan or stirring, until the shiitakes are starting to soften, about 5 minutes. Stir in the tamari and cook 5 minutes longer, until the shiitakes are tender. Add to the pumpkin.
Step 5Deglaze the skillet with one-half cup of the stock, scraping the bottom, then pour it into the Dutch oven. Pour the remaining 1 tablespoon of oil into the skillet and add the chorizo. Saute briefly, then add the leeks and garlic and cook, stirring constantly, until soft, 5 to 7 minutes. Add to pumpkin and shiitakes. Deglaze pan again with another one-half cup of stock and scrape into the Dutch oven. Add the diced poblano, sage and remaining 1 cup of stock and mix well. Taste and adjust seasoning.
Step 6Cover the pan and bake, stirring occasionally, until the largest cubes of pumpkin are tender but not falling apart, 35 to 45 minutes. Serve immediately, in shallow bowls.