1. First make the stock: Place all the ingredients in a saucepan with 2 quarts cold water. Bring to a boil and then simmer for as long as possible to bring out the flavor, 2 to 3 hours if you can. Strain the stock and set aside.
2. Preheat the oven to 300°F.
3. Place a casserole dish over high heat, melt the butter, and add the lamb. Season with salt and pepper and stir until it is a nice brownish color. Transfer to a plate and repeat the process with the vegetables, before also transferring them to a plate.
4. Spoon all the vegetables, the lamb, and the pearl barley into the casserole dish, placing the potatoes on top (you do not want them to get mushy). Remove all the leaves from the thyme stems (discard the stalks) and add them to the dish. Cover with the hot lamb stock and place in the oven for 1 1/2 hours.
5. While the lamb stew is cooking, make a roux: Melt the butter in a saucepan and beat in the flour, until it forms a paste. Once the casserole has cooked, ladle the juices from the stew into a saucepan and slowly beat into the roux. Cook, stirring, until thickened and smooth. Then pour the thickened gravy back into the stew before serving.
Excerpted from Clodagh’s Irish Kitchen, A Fresh Take on Traditional Flavors by Clodagh McKenna. Published by Kyle Books. Photography by Tara Fisher.