Place the ancho, pasilla, and New Mexico peppers in a dry pan over medium heat. Toast them for about one to two minutes on each side until they soften and smell nutty. This enhances their natural oils and deepens the chili’s flavor.

Let the toasted peppers cool. Remove the stems and shake out the seeds. Place the peppers in a bowl of hot water and soak for 20 minutes until they soften. Move the peppers to a food processor, add a cup of soaking water and a pinch of salt. Blend until smooth, then set the paste aside.

In a large bowl, mix beef chuck cubes with cumin, salt, and pepper. Heat a tablespoon of oil in a big pot over medium-high heat and add the beef in a single layer. Sear the meat for 6 to 7 minutes, turning it occasionally until it browns on the outside. Remove the beef and place it on a plate.

Pour the remaining oil into the same pot. Add chopped onion, jalapeños, and serranos. Cook for about 5 minutes, stirring occasionally, until the onion becomes soft and slightly golden. Add garlic and cook for one more minute.

Return the beef to the pot with the chili paste. Mix everything and cook for 2 to 3 minutes to blend the flavors. Add beef stock, water, brown sugar, Worcestershire sauce, and masa harina. Stir well and bring to a quick boil.

Lower the heat, cover the pot, and let the chili simmer for about 2 hours. Stir every 30 minutes and check the beef for tenderness near the end. If the pot looks too thick, add a splash of water. If it looks too thin, stir in more masa harina.

Once the beef easily falls apart with a fork, the chili is ready to serve.