Heat a large saute pan over high heat. When the pan is hot, add 1 tablespoon of the butter and the beef and sear on both sides until golden brown, about 3 to 4 minutes per side. Remove from the pan and set aside.

To the same pan, add the diced onion and carrots and saute until the onions begin to soften, about 5 minutes. Add the wild mushrooms and cook lightly to release the flavors of the vegetables. Add the Guinness and bring to a boil. Add in the stock and bring to a boil. Place the baby onions into the sauce. Bring to a simmer and reduce by half.

Return the beef to the pan and cook to desired doneness.

To serve, first remove the mushrooms and vegetables from the sauce and arrange in the middle of a large dish. Place the beef on top of the vegetables in the middle of the plate. Arrange the onions around the plate. Bring the sauce back to the boil and add the rest of the butter to the pan. Mix until it is all blended in, then add the chopped parsley into the sauce, and pour as much sauce over the beef as you want.