Preparation Heat a dry 10" skillet, preferably cast iron, over medium-high. Rub steak with 1 Tbsp. oil, then season all over with 1 tsp. salt and 1/2 tsp. pepper. Cook, turning every 2 minutes and making sure to get color on the fat cap, until browned on all sides and medium-rare (an instant-read thermometer inserted into the center should register 120°F), 10–15 minutes. Transfer steak to a plate. Pour off oil from skillet, leaving crispy bits behind. Heat remaining 2 Tbsp. oil in same skillet over medium-high. Add mushrooms and cook, stirring occasionally, until golden brown and beginning to crisp, 6–8 minutes. Add garlic, season with 1 tsp. salt and 1/2 tsp. pepper, and continue to cook until mushrooms are well browned and garlic is fragrant, 3–4 minutes. Meanwhile, cook noodles in a large pot of boiling salted water, stirring occasionally, until al dente. Drain and return to pot. Add butter, lemon zest, and lemon juice; season to taste with salt and pepper. Stir brandy and 1/2 cup water in a small bowl. Add to mushroom mixture and cook, stirring occasionally, until reduced by half, about 2 minutes. Remove from heat, then add cream, Worcestershire, and mustard and stir to combine. The heat of the pan will reduce and thicken the sauce slightly—if it doesn’t, cook over medium-low heat for about 1 minute. Stir in sour cream until combined and warmed through. Slice steak against the grain into 1/2"-thick slices. Divide noodles among plates. Top with steak, creamed mushrooms, and dill, then season with a few cranks of pepper.
Preparation Heat a dry 10" skillet, preferably cast iron, over medium-high. Rub steak with 1 Tbsp. oil, then season all over with 1 tsp. salt and 1/2 tsp. pepper. Cook, turning every 2 minutes and making sure to get color on the fat cap, until browned on all sides and medium-rare (an instant-read thermometer inserted into the center should register 120°F), 10–15 minutes. Transfer steak to a plate. Pour off oil from skillet, leaving crispy bits behind. Heat remaining 2 Tbsp. oil in same skillet over medium-high. Add mushrooms and cook, stirring occasionally, until golden brown and beginning to crisp, 6–8 minutes. Add garlic, season with 1 tsp. salt and 1/2 tsp. pepper, and continue to cook until mushrooms are well browned and garlic is fragrant, 3–4 minutes. Meanwhile, cook noodles in a large pot of boiling salted water, stirring occasionally, until al dente. Drain and return to pot. Add butter, lemon zest, and lemon juice; season to taste with salt and pepper. Stir brandy and 1/2 cup water in a small bowl. Add to mushroom mixture and cook, stirring occasionally, until reduced by half, about 2 minutes. Remove from heat, then add cream, Worcestershire, and mustard and stir to combine. The heat of the pan will reduce and thicken the sauce slightly—if it doesn’t, cook over medium-low heat for about 1 minute. Stir in sour cream until combined and warmed through. Slice steak against the grain into 1/2"-thick slices. Divide noodles among plates. Top with steak, creamed mushrooms, and dill, then season with a few cranks of pepper.