Step 1

1 In a large skillet over medium-high heat, heat the oil and melt the butter

Step 2

2 Add the onion and cook, stirring, until the onion begins to soften, about 3 minutes

Step 3

3 Add the garlic and cook, stirring, until fragrant, 1 minute more, then add the mushrooms, salt and pepper and stir to combine

Step 4

4 Cook until the liquid released by the mushrooms evaporates and the onions and mushrooms wilt, 7 to 10 minutes, stirring occasionally

Step 5

5 If the mushroom mixture starts to stick to the bottom of the pan, decrease the heat to medium

Step 6

6 Add the sherry and thyme and stir to combine, scraping up any bits stuck to the bottom of the skillet

Step 7

7 Decrease the heat to low and simmer, stirring a couple of times, until the sherry evaporates, 3 to 5 minutes

Step 8

8 Stir in the cream, then taste and adjust seasonings, if needed

Step 9

9 Let the mushrooms simmer for about 2 minutes

Step 10

10 Remove the sauce from the heat

Step 11

11 Make the steak: Pat the meat dry and sprinkle with salt, pepper and thyme, if using

Step 12

12 In a large cast-iron skillet over medium-high heat, heat the oil until shimmering

Step 13

13 Add the steak and cook, undisturbed, 2 to 3 minutes per side for medium-rare

Step 14

14 The meat should be just charred

Step 15

15 Transfer the steak to a cutting board, let rest for 2 minutes and slice each piece thinly against the grain

Step 16

16 Divide the steak among plates

Step 17

17 Spoon creamed mushrooms on top and sprinkle with more fresh thyme leaves, if using

Step 18

18 Serve warm