Preparation

1. To make the salsa del valle: In a 10-inch cast-iron skillet over medium-high heat, warm 2 tablespoons of the olive oil. Add all the chiles and cook until toasty and burning your nostrils a bit on an inhale, about 2 minutes. They should turn a darkish brown color.
2. Add the almonds, pine nuts, and garlic and cook for about 3 minutes, or until golden brown. Slide these ingredients into the blender. Add the vinegar and remaining 10 tablespoons olive oil and puree it to death—on high speed for about 5 minutes. Let cool, then season with kosher salt, add the cashews, and mix with a spoon. Set aside.
3. For the Poke: If you’ve got a loin, trim the bloodline (the darker part) and remove the skin. Lay the fish on a dampened kitchen towel and use a knife to pull off the dark matter and impurities. Flip the fish flesh-side down. On the top, make a small incision between the skin and the flesh. Use another towel to pinch the end so the fish doesn’t slide off when you’re removing the skin. Work the knife slowly away from you, pulling the skin up from the flesh. Discard the skin.
4. Dampen a kitchen towel and wipe a very sharp knife on both sides so it’s clean and also a little wet—this will help it cut through the flesh cleanly. Using strong single strokes, cut the fish into 11⁄2-inch cubes. Set aside. In a bowl, vigorously whisk together the miso, soy sauce, yuzu juice, sesame oil, and olive oil. Fold in the tuna so it’s completely coated. Season with furikake. Set the poke aside.
5. To Finish: Line a wire rack with paper towels. In a 10-inch cast-iron skillet over medium-high heat, warm the vegetable oil to about 375°F. Add the tortillas and fry until crispy, about 30 seconds per side. Or, put the tortillas right over the flame of the range until they’re blistering and dry. Season your tortillas with kosher salt after pulling them from the oil or fire. Let them cool on the prepared rack until they’re slightly warmer than room temperature. (You can also buy tostada shells.)
6. In the meantime, prepare an ice-water bath in the largest mixing bowl you have by stirring together water and a tray of ice. Cover a plate with paper towels. Set both aside.
7. Wearing gloves, flip the sea urchins over onto a kitchen towel or a rimmed baking sheet, with the mouth facing up. Take a hard metal spoon in each hand, with the lips facing out—as if you’re playing the spoons. Force one spoon into the hole. Tap down on it with the other spoon gingerly until you hear a crack. Then jam them both in and, working the spoons in a pruning-shear motion, crack open each sea urchin. It’ll be messy, which is why you have it all laid out on a kitchen towel. Rinse your spoons and carefully scrape the yellow sea urchin roe away from the shell. There should be five portions. Take care not to break up the roe, each portion should come off in a piece, like a small, long tongue. Put these pieces into the ice-water bath to clean off any impurities. Set the sea urchin roe on the prepared plate and, using tweezers, remove any more impurities.
8. Place a layer of tuna poke on each tostada, then add salsa (as much as you want for how spicy you like it), scallions, one or two pieces of sea urchin roe, a sprinkle of furikake, and a squeeze of lime juice. I like to hit it with a pinch of sea salt at the end. Serve immediately.