Adjust the oven rack to the middle position and heat oven to 400°F. Line a baking sheet with foil and coat lightly with vegetable oil spray.

Combine the panko and vegetable oil in a small skillet over medium heat. Cook, stirring frequently, until the crumbs are golden brown and smell toasted, about 3 to 5 minutes. Transfer to a small bowl and set aside to cool.

Cut the jalapeños in half lengthwise. Using a small spoon, scrape out the seeds and ribs—if you want more heat, reserve the seeds and add them into the filling later.

Combine the cheddar, cream cheese, scallions, lime juice, chili powder, and salt in a bowl. Mash the mixture together with a fork until it is uniform and creamy.

Fill each jalapeño half with the cheese mixture, smoothing the top. Press the toasted panko firmly into the cheese on each pepper so the topping adheres.

Arrange the peppers on the prepared baking sheet. Bake until the filling is hot and bubbling and the peppers are just tender, about 10 to 12 minutes. Serve hot.