An hour before you are going to cook the brisket, take the meat out of the refrigerator. Rub the meat with the salt, pepper and thyme all over and let stand.
In a large deep pan, wide enough to hold the brisket in 1 piece, heat the butter over medium-high heat and brown the meat on both sides. Remove to a plate.
Add the onions and carrots to the pan and cook over low heat for about 15 minutes, until the onions are limp and browned slightly. Add the mustard and stir to combine.
Turn up the heat to high and add the stock and beer. Stir well. Add the thyme sprigs. Place the brisket on top of the vegetables, with the fat side up. The liquid should come up the sides of the meat, but not cover it. Add a little stock or water if you need to.
Cover the pot and make sure you have a good seal. You can first put plastic wrap over the pot, and then the lid for a perfect seal (the plastic will not melt).
Turn the heat to your lowest simmer setting.
Check the meat after 2 hours, by slicing and tasting a small piece. If still too chewy, cook another 15 minutes and check again. When meat is tender, turn off the heat.
Ladle off all the juices (but not the vegetables) into a measuring cup or fat separator cup. Let sit until fat rises to surface. Pour juices back into pan, leaving fat behind. Put lid back on until ready to reheat for serving.
Make the Warm Potatoes with Parsley (see recipe).
Slice the meat against the grain (should be the short side of the brisket). Place some potatoes on a plate. Drape the meat slices next to the potatoes. Spoon a generous serving of the carrot-onion-sauce over the meat.
Recipe by Jane O'Riordan
Terre Rouge and Easton Wines