Cover the potatoes with water and bring to a boil. Salt the water and cook the potatoes to tender. Drain, return to the pot and mash with milk, sour cream, cream cheese, chives, garlic, half the chopped jalapeños or chili peppers, some pepper and the egg yolk. Cover the pan to keep the potatoes warm.
Heat the oil, two turns of the pan, over medium-high heat. Pat the meat dry and add to the hot pan; brown and crumble, then season with salt, pepper, chili powder, cumin and coriander. Stir to toast, then add the onion, garlic and remaining jalapeños or chili peppers, Worcestershire and tomato paste. Stir for 1-2 minutes, then add the beer. When the beer almost evaporates, add the stock and cornmeal and beans, if using, and simmer to thicken over low heat.
Place a rack in the center of the oven and turn on the broiler.
Transfer the beef chili to a casserole or individual bowls. Using a pastry bag or large food storage bag, pipe the potatoes on top of the chili. Transfer to the broiler to brown the potatoes. Top with pickled jalapeños and serve.