Wash the kale leaves and remove stems. Parboil (2 mins) or steam (4 mins) kale leaves, run under cool water, drain and allow to cool. Chop kale into bite-sized pieces and set aside.
Heat oil in a large pan over low heat, then add butter to melt. Add the onions and jalapeno or pepper flakes (unless chorizo will provide enough heat). Saute until onions are soft.
Add coriander seeds and saute a few minutes until fragrant. Add ¼ cup of finely chopped chorizo and stir to combine (mixture should turn a slightly red color). Add garlic and cook for one minute.
Increase heat to medium, and add butternut squash (and sweet potato chunks if using) and saute for 5 minutes with the onions.
Add enough chicken stock to fully cover vegetables, along with the herbs. Cook on low heat until veggies are tender.
Turn off heat and cool to room temperature. ONLY when soup is cooled, using a regular or immersion blender, blend soup until creamy. CAUTION: When using a regular blender, do very small batches even with room temperature soup only (or cooler) and hold the top on securely, to avoid it popping off and you getting burned.
While the soup is cooling, saute the chorizo in a separate frying pan over medium heat until just browned; don’t overcook it. Use the edge of a spatula to break the chorizo into smaller chunks. Set this aside and don’t remove the juice/oil that the chorizo is sitting in!
Return blended soup to medium heat and add kale, cooked chorizo and half of the rendered chorizo-liquid (reserve the rest). Lower heat to simmer for 10-15 minutes. Add more of the chorizo-liquid to suit your taste (save a little for garnish). Don’t be afraid of a little oil - it will add flavor! Add sherry and simmer for a few more minutes. Season with salt and pepper to taste.
Turn off heat and stir in handful of chopped cilantro. Serve soup garnished with a few whole cilantro leaves, and a drizzle of remaining chorizo oil if desired.