For the Sherry Vinaigrette
2 In a mason jar, combine the olive oil, vinegar, shallot, garlic, honey, mustard, salt and pepper. Seal with a lid and shake vigorously until emulsified, around 15 seconds. Taste the vinaigrette for seasoning and adjust with salt and pepper as desired. Cover and refrigerate up to 5 days.
For the Steak and Salad:
5 Remove the steak(s) from the fridge and let sit at room temperature 30 minutes before cooking. Pat the steak(s) very dry with paper towel and generously season both sides with sea salt. Set aside.
6 Add the pancetta to a large, dry, carbon-steel or cast-iron skillet. Place the pan over medium-high heat and cook, stirring occasionally, until the pancetta is crispy, around 5 minutes. Using a slotted spoon, transfer the pancetta to a plate lined with paper towel to absorb excess grease. Discard all but 1 tablespoon of rendered fat in the pan.
7 If the steaks have released surface moisture, pat them dry with paper towel and carefully transfer them to the hot skillet. Cook, undisturbed, over medium-high heat until a deep crust has formed, around 4 minutes. Flip the steak(s) and push it to the top edge of the skillet. Reduce the heat to medium and add the butter, garlic and thyme to the bottom half of the skillet. Carefully tilt the pan towards you so that the melted butter pools and use a large spoon to continuously baste the steak(s) until the thickest part reaches 130F for a medium-rare centre or 145F for medium.
8 Once the steaks are cooked to your preferred doneness, transfer them to a sheet pan lined with a wire rack and let them rest at least 8 minutes before slicing against the grain into thin pieces.
9 On a large serving platter, arrange the frisée, radicchio and Belgian endive. Top with the pancetta and drizzle with the vinaigrette. Arrange the sliced steak overtop and garnish with shaved pecorino Romano. Serve immediately.
