Toast guajillo, ancho, and pasilla chiles in a non-stick skillet on medium-high heat. Stir occasionally until darkened and slightly softer (about 3 minutes).
Place softened butter in stainless steel bowl and mix with 2 cups boiling water. Drain and throw away seeds and stems.
Heat 1 tbsp oil in a large pot on medium-high.
Rub chuck, short ribs, and brisket with salt and pepper.
Stirring occasionally, cook until browned (about 5 minutes). Continue cooking until liquid all liquid has evaporated from pot (about 8–10 minutes more). Place beef onto plate.
Heat remaining 1 tbsp oil in same pot.
Add onions and garlic; season with more salt and pepper. Cook until onions are softened, stirring often (about 6–8 minutes). Beef may stick to the pot, so add splash of water (stirring occasionally) to scrape up left over browned bits of beef.
Add cumin, oregano, and chipotle. Cook for 1 minute while stirring occasionally.
Transfer the whole mixture to your slow cooker (4–6-quart).
Add lager, beef, and chile purée, season with salt and pepper. Stir.
Cover slow cooker and heat until meat is very tender (about 7–8 hours on low or 4–5 hours on high). If the mix seems too thin, simmer until thickened to desired consistency.
Taste and season if needed. Serve dish topped with sour cream, cheddar, red onion, cilantro leaves, and chips.