Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Slice the jalapeño peppers in half lengthwise and use a spoon to carefully scrape out the seeds and membranes.
In a medium mixing bowl, combine the shredded chicken breast, shredded cheddar cheese, and half of the garlic and onion powders.
Fill each jalapeño cavity generously with the chicken and cheese mixture, pressing down firmly to ensure it stays in place.
In a small shallow bowl, whisk the egg; in a separate shallow bowl, place the panko breadcrumbs.
Dip the stuffed side of each jalapeño into the egg wash, then press into the panko until a thick layer adheres to the top.
Arrange the peppers on the prepared baking sheet and bake for 15 to 18 minutes until the coating is golden and the peppers are tender.
While the poppers bake, whisk together the Greek yogurt, lemon juice, dried dill, sea salt, black pepper, and remaining garlic and onion powders.
Serve the hot poppers immediately with the cool ranch dip on the side.