Brown the meat in butter and oil. Season with salt and pepper. Set aside.
Slice the potatoes, parsnips, carrots, onions and garlic, and brown the vegetables together with the mushrooms. Add the meat.
Add the beer, and cover the rest of the stew with water.
Add the stock cube and make sure it dissolves completely. Let it simmer for about one hour. The meat should be very tender.
Mix a couple of tablespoons of corn starch with about as much water. Pour it in and make sure to stir so that you do not get lumps in the stew.
Garnish with parsley and thyme.