In a large bowl, combine the pork, basil, garlic, green onions, fish sauce, sriracha, sugar, cornstarch, pepper, and salt. Form the pork mixture into 4 even patties about ⅓-inch thick.

In a small bowl, whisk the mayonnaise, green onions, and sriracha together until smooth to make the sriracha mayo.

Heat the sesame oil in a large cast iron skillet over medium heat. Add the pork patties and cook undisturbed until browned and the center reaches 160°F, about 5 minutes each side.

Spread 1 tablespoon of the sriracha mayo on the toasted side of the top and bottom buns. Divide the pickled vegetables, cilantro, and jalapeno (if using) between the bottom buns.

Top with the pork patty, cucumbers, and the top bun, sauce side down. Repeat with remaining ingredients. Serve warm.