Trim mushroom stems and then chop them into a small dice. Yes, this is a total fucking pain. So you may want to double the recipe. But I don't blame you for cursing my name while doing this.
Dice red onion and red pepper. Mince garlic.
Add 2 tablespoons of olive oil to a large sauté pan and warm it over a medium-high heat. Add in the onion, peppers, and garlic. Cook for a minute, just so that the mixture is aromatic.
Add in chopped mushrooms in batches. You may still be cursing my name. The key here is to not crowd the pan. A crowded pan will cause more liquid to accumulate and make the mushrooms soggy. Once one batch cooks down, keep adding in more.
Cook until the mushrooms are reduced in size by at least a half.
Add in the ketchup, brown sugar, chili powder, mustard, red pepper flakes, hot sauce, and Worcestershire sauce. Stir to combine. If you like your Joes saucy, you may want to adjust this part of the recipe by 25%.
Cook until the mixture is well combined and hot.
Serve on a Kaiser roll. Then motorboat the heck out of these guys, they are hella good!