Heat beer and beef stock to a boil in a small pot. Take the pot off the heat and add the mushrooms. Allow mushrooms to steep for 30 minutes. Strain mushrooms and reserve mushroom/beef/beer broth. Roughly chop the mushrooms.
Preheat oven to 425°F Put ground beef and pork in a mixing bowl.
Heat butter in a small skillet and add the onions. Cook, stirring, until onions have wilted. Add the mushrooms and continue cooking for 3-4 minutes. Season with salt and pepper, cook for an additional minute and remove from heat. Let cool briefly and add the onion and mushroom mixture to the meat.
Add the mushroom/beef/beer broth, eggs, bread crumbs, parsley, chopped thyme, and salt and pepper. The mixture should feel very moist, if it feels dry, pour in some additional beer. Do not over-mix. Pack into a 2½ by 4½ by 8½ inch loaf pan and bake for 40 minutes.
While meatloaf is cooking, prepare the glaze by mixing together the ketchup, honey, and mustard until well incorporated.
Remove from the oven and add glaze to the top of the loaf. Return to the oven and bake an additional 5-10 minutes until glaze has browned.
Remove the meatloaf from the oven and allow to rest at least 20 minutes. Pour out any rendered fat from the pan, slice and enjoy with your favorite Harpoon beer.
Boston based Sebastians also recommends that this dish makes a great sandwich!