Prep ingredients: Peel and finely chop 1⁄2 of the ginger (save rest for own use). Peel and finely chop 2 cloves garlic. Coarsely chop cilantro leaves and stems. Thinly slice jalapeño and discard stem
Pickle carrot & cucumber: Grate carrot on the large holes of a box grater (no need to peel). Thinly slice cucumbers into rounds. In a medium bowl, combine vinegar, chopped ginger, 1⁄2 of chopped garlic, 1 tablespoon sugar, and 1⁄2 teaspoon salt, whisking to dissolve. Add carrots and cucumbers and let sit until step 6, stirring occasionally.
Dry brine steaks: Split steaks horizontally and pound to a 1⁄4-inch thickness with a meat mallet or heavy skillet and rub with oil. Sprinkle with remaining garlic, 1 teaspoon salt, and several grinds pepper and let sit until step 5.
Toast rolls: Heat a grill or grill pan over high. Split rolls. Reduce heat to medium high. Open rolls and grill, cut-sides down, until lightly toasted, about 2 minutes. Flip rolls and grill, turning once or twice, until outsides are lightly toasted, 1– 2 minutes (watch closely).
Grill steaks: Rub grill or grill pan grates with oil. Add steaks and cook over medium-high until lightly charred about 11⁄2 minutes. Flip and cook just 1 minute more. Transfer to a plate (or cutting board to slice if desired).
Assemble & serve: Spread mayo on rolls and top each with 2 steaks. Use a slotted spoon to add some of the pickled carrots and cucumbers to sandwiches. Garnish with jalapeños and cilantro. Close sandwiches and serve with remaining pickled veggies alongside. Enjoy!