For this dish I prepare potato gnocchi which are poached in stock or salted water, then dried and fried or grilled until golden. Doing it this way makes the gnocchi easier to handle.
Season the meat on all sides then brown well all over in hot olive oil over a high heat. Place on an oven tray. Put aside.
Thinly slice the onion then sauté in the same pan that the meat was browned in. Add the Guinness, bring back to a steady simmer then reduce by half. Pour into a clean pot then add the demi and the thyme. Bring to the simmer for a minute or so. The sauce should be a coating consistency.
Remove from the heat; discard thyme. Place sauce aside until required.
Cover the potatoes with salted water, then cook over a steady heat until tender. Strain off the water then return the potatoes to the heat to dry off. While they are still hot, mash or preferably put them through a mouli. Allow to cool.
Beat the butter into the mashed potato, then the egg. Mix in the flour.
Carefully blend in the horseradish. Place the mixture onto a floured surface, then knead once or twice. Using flour to prevent sticking, carefully roll out to a thickness of 5mm. Alternatively, shape into a cylinder (4 cm diameter) then slice into 1 cm discs.
Using a 4cm plain cutter, cut out 12 discs, placing them on a floured tray as you go.
Bring a large pot of salted water to the boil. Cook the gnocchi in batches, dropping them into the water and cooking for 2 ‐ 3 minutes, or until they float. Drain each batch, then place on a lightly buttered baking tray. Cover with a piece of buttered greaseproof paper, then place aside until the next step.
The gnocchi may be sautéed to golden, or grilled at this stage, then reheated as required. Or you can reheat them as they are.
Finish the steaks all together on the one tray in a hot oven, preheated to 200°C, turning them half way through the cooking time. Or finish them individually, in the pan, turning them once.
Lightly brown the gnocchi in a little hot oil in a pan, or reheat them in the oven until they just begin to puff up.
Bring the sauce to the boil and skim if need be. Season to taste, then reduce the heat and whisk in the butter.
Arrange the steak on a hot dinner plate, placing one or two discs of gnocchi on top. Spoon over the rich Guinness sauce and sprinkle over the chopped chives.
Serve immediately, accompanied by braised cabbage and glazed root vegetables.