For dinner on Saturday I used a ‘Modernist’ approach based on this NY Times article. You start by freezing the steak to lower the core temperature then searing on one side before transferring to the oven at a low temperature with a probe to monitor the core temperature.
Unlike the instructions, I let the internal temperature rise to about 62°C, somewhat above the 50°C suggested in the article. It was soft and tasty and I think I could afford to stop at a lower temperature although I don’t know if I would go quite as low as the recipe.
A video demonstration, also from the NY Times, can be seen on their site.