Instructions
1Read the total time before you start this one: it is about an hour and a half door-to-table, and the potato track is strictly sequential. This is the Friday night of the week, or the night you take the microwave shortcut in step 2. Begin by taking the steaks out of the fridge, patting them completely dry, and salting them on all sides. Leave them uncovered on a rack or plate at room temperature while you do the potatoes — 40 minutes of dry, salted rest is most of what makes a good crust.
2Heat the oven to 450°F. Put the potatoes in a pot of well-salted cold water, bring to a boil, and simmer 18-20 minutes until a fork slides in with no resistance. Undercooked potatoes will not smash. TO CUT ABOUT 20 MINUTES: skip the boil entirely — prick the potatoes, microwave them on a plate 10-12 minutes until a fork slides in, then let them steam dry 5 minutes and smash and roast as written. You lose a little of the fluffy interior boiling gives you, but the crisp edges, which are the whole point of a smashed potato, are identical.
3Grate the garlic fine and stir it into about a teaspoon of lemon juice; let it sit while you get the potatoes going. Ten minutes in acid takes the raw acrid edge off garlic — straight raw grated garlic on hot steak is harsh, and it is the part your 3-year-old will push away. Then mash it with the butter, parsley, thyme, and salt in a small bowl with a fork. Set it aside at room temperature so it is soft enough to melt on contact later.
4Drain the potatoes and let them steam dry 5 minutes, then spread them on an oiled sheet pan and press each one flat with the bottom of a glass until it cracks open, about half an inch thick. Drizzle with the olive oil, season, and roast 25-30 minutes until the edges are deep brown and crisp. Add the rosemary in the last 5 minutes so it does not scorch.
5While the potatoes roast, pat the steaks dry one more time and add the pepper. Turn the vent hood on high before the oil goes in, and open a window — a cast iron sear with a 450°F oven already running will set the smoke alarm off, and that is a bad thirty seconds with a toddler in the house. Heat the neutral oil in a heavy skillet or cast iron over high until it just begins to smoke.
6Lay the steaks in and do not move them for 3-4 minutes, until a hard brown crust forms. Flip and go another 3-4 minutes for medium-rare, which is 130°F on a thermometer in the thickest part. Pull them at 125°F — they climb about 5 degrees while resting.
7Move the steaks to a board, put half the garlic-herb butter on top, and rest them 6-8 minutes — a 1-inch steak needs that long and no longer, because at 10 minutes it is merely warm. Resting is not optional; cutting early dumps the juice onto the board.
8While the steaks rest, use that same hot skillet for the peppers — but look at the bottom first. If the fond is brown, pour off all but a thin film of the rendered beef fat and skip the olive oil entirely; there is more than enough fat in that pan already, and the peppers will pick up everything the steak left behind. If the fond has gone black, wipe the skillet out with a paper towel and use the 1 tbsp olive oil instead — scorched fond is bitter and it goes straight into the peppers. Add the pepper strips and cook 5-6 minutes over high heat without stirring much, until they blister and take on black spots. Finish with flaky salt and a hard squeeze of the half lemon. Do not skip the lemon: it is the only bright thing on the plate, and without it the beef, the butter, the oil-roasted potatoes and the oil-blistered peppers all read as one heavy note.
9Slice the steak thin against the grain, spoon the resting juices back over it, and serve with the smashed potatoes, the blistered peppers, and the rest of the garlic-herb butter at the table.