1. Preheat the oven to 300°F (150°C/Gas mark 2).
2. Heat 3 tablespoons of the olive oil in a Dutch oven or flameproof casserole dish over medium-high heat. Add the mushrooms, season with salt and pepper, and toss for 2 to 3 minutes, until lightly golden. Remove the mushrooms from the pan with a slotted spoon and set aside.
3. If there isn’t much oil left in the dish or pan, add another tablespoon. Tip in the onions and garlic, stir over the heat, season with salt and pepper, and cook for 4 to 5 minutes, until they start to turn golden at the edges. Add the meat and wine and 2 teaspoons of the thyme leaves. Bring to a boil and cover with a lid.
4. Bake in the oven for 1 1/4 to 1 1/2 hours, until the meat is just tender. Take the pan out of the oven and turn up the heat to 450°F (230°C/ Gas mark 8). Stir in the mushrooms and red wine vinegar. Arrange the potato slices over the beef in the pan (it’s fine if there’s more than one layer). Scatter over the remaining 1 teaspoon thyme and some salt and pepper, then dot with the butter.
5. Return the Dutch oven to the (now hot) oven and bake for another 30 to 40 minutes, or until the potatoes are cooked through and beginning to turn golden. Bring to the table and serve.
Reprinted from Rachel's Irish Family Food: 120 Classic Recipes From My Home to Yours Copyright © 2013 by Rachel Allen. Published by Harper Collins Publishers. Available everywhere books are sold.