Scrape the vegetables into a 4- to 7-quart slow cooker and add the drained beef, diced tomatoes, strained tomatoes, beer, black beans, chipotle chile, tamari, maple syrup, chile powder, cumin, oregano and cacao powder. Season with salt and pepper, and stir to combine. Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours. Season with salt and pepper to taste.