Step 1

Put the potatoes in a medium pot and cover with cold water by 1 inch; season with salt. Bring to a boil and cook until fork-tender, 15 to 20 minutes; drain.

Step 2

Meanwhile, combine the parsley, scallion, jalapeno, garlic, lemon zest and juice, 2 tablespoons olive oil and 1/2 teaspoon salt in a mini food processor; pulse until finely chopped. Transfer to a small bowl and set aside.

Step 3

Heat a large skillet over high heat and add 1 tablespoon olive oil. Season the steak with salt and pepper. Add to the skillet and cook until browned, 5 to 6 minutes per side for medium rare. Transfer to a cutting board and let rest 5 minutes.

Step 4

Add the remaining 1 tablespoon olive oil and the potatoes to the same skillet; gently smash the potatoes with the back of a wooden spoon. Cook, stirring occasionally, until golden brown and slightly crisp, about 5 minutes. Season with salt and pepper.

Step 5

Thinly slice the steak against the grain. Top with the parsley sauce and serve with the potatoes.