Place washed and deseeded dried New Mexico chiles in a medium stockpot with 3 cups of water. Bring to a boil, then remove from heat and let steep for about 30 minutes until soft. If needed, place a plate on top to keep chiles submerged.

While chiles soak, trim excess fat from beef chuck roast and cut into bite-sized chunks.

In a bowl, combine flour, kosher salt, and black pepper. Dredge each piece of beef in this seasoned mixture until coated.

Heat olive oil in a pan and brown the beef chunks until they develop a crust. Work in batches if necessary to avoid overcrowding.

Strain the softened chiles but reserve the cooking liquid. Blend the chiles with some of this liquid until smooth, adding more liquid as needed for consistency.

For the silkiest texture, pass the chile puree through a fine mesh strainer to remove any remaining seeds or tough skin bits.

Place chopped onion at the bottom of a 4-6 quart crockpot, then add the browned beef chunks.

Pour the strained chile puree over the beef. Add enough beef stock to just cover the meat.

Set crockpot to low for 8-10 hours or high for 4-5 hours, until beef is tender and flavors have melded.

If desired, add chili powder to taste toward the end of cooking for additional heat.