Smooth Chicken Vindaloo

• 900 g chicken tenderloins (unbreaded), cut into 2-3 pieces each
• 10-12 whole dried Kashmiri chilies, stemmed and most seeds shaken out
• 4-6 dried chiles de arbol, stems off, seeds left in
• 2 medium yellow onions (~300 g), sliced thin
• 1 whole head garlic (~50 g), peeled
• 25 g fresh ginger (frozen is fine, grates easily)
• 2 tsp ground cumin
• 1 tsp ground turmeric
• 1 1/2 tsp garam masala
• 2 tsp kosher salt
• 1 tsp light brown sugar
• 60 ml apple cider vinegar, plus up to 10 ml more to finish
• 1 tbsp neutral oil (~14 g)
• 1 tsp black mustard seeds
• 200-300 ml water, to loosen

Method

1. 1
   Soak the chilies

   Stem the Kashmiri chilies and shake out most of the seeds; they blend gritty otherwise. Leave the arbols whole with seeds in - that is where the heat comes from. Cover both in just-boiled water and leave 20 minutes until pliable. Reserve the soaking liquid.

2. 2
   Brown the onions

   In a Dutch oven over medium heat, cook the sliced onions until deeply browned, 15-20 minutes. Not translucent - browned. This sweetness is the counterweight to all the vinegar and there is no substitute for it. Scrape them into the blender and leave the fond in the pot.

3. 3
   Blend the paste

   Drain the chilies and add to the blender with the browned onions, garlic, ginger, cumin, turmeric, garam masala, salt, brown sugar and 60 ml of the vinegar. Blend smooth, starting low and ramping up. If it stalls, use the tamper or add soaking liquid a spoonful at a time - not more vinegar. You want it thick and pourable, not runny. Open the lid away from your face; the arbols aerosolize.

4. 4
   Pop the mustard seeds

   Heat the oil in the same Dutch oven over medium-high. Add the mustard seeds and wait for them to pop - about 30 seconds of audible crackling. They need bare hot oil to do this; added with the paste they just stew and stay bitter.

5. 5
   Fry the paste (bhuna)

   Add all the paste and fry 6-8 minutes, stirring, until the raw garlic smell is gone and oil begins to separate at the edges. This is the step that separates good vindaloo from spiced vinegar - do not rush it. It will spit; keep the lid partly on and use a long spoon.

6. 6
   Simmer the chicken

   Add the chicken and enough water to bring it to a sauce consistency, 200-300 ml. Simmer 12 minutes, maximum 15. Tenderloins are lean and cook fast - the whole reason the sauce is built first is to keep their time in it short.

7. 7
   Finish

   Taste. Some acid cooks off during the simmer, so add the reserved vinegar 5 ml at a time if it needs sharpening. Correct salt. Serve over basmati.