Season the chuck roast with salt and pepper and sear in a heavy-bottomed pot until golden brown and crispy on all sides. Remove from the pot. Repeat the process with the brisket.
Once both roasts have cooled to room temperature, dice the meat into ½-inch pieces. Heat up the heavy-bottomed pot and cook the diced meat in batches until caramelized. Remove and set aside.
Add olive oil to the pot and sauté the onions, jalapeños, and spices. Add tomatoes and poblanos and cook for 3 minutes. Add beef back to pot, cover with beer, and stir to incorporate. Cover the pot and let it simmer for 3 hours, stirring occasionally.
When ready to serve, garnish with grated cheddar cheese, pickled jalapeños, and diced red onions, if desired.