Step 1: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper or spray lightly with non-stick cooking spray. Carefully wash and dry all jalapeños. Slice each jalapeño in half lengthwise. Using a small spoon or jalapeño corer, meticulously scoop out all the seeds and white membranes. (Wear gloves to protect your hands from capsaicin.)
Step 2: In a medium mixing bowl, combine the softened cream cheese, shredded sharp cheddar cheese, garlic powder, onion powder, salt, and black pepper. Mix until well combined and smooth.
Step 3: Using a small spoon, fill each jalapeño half with a generous amount of the cream cheese mixture, gently pressing it into the cavity.
Step 4: Set up your breading station. Place the all-purpose flour in the first shallow dish. In the second dish, whisk the egg with 1 tablespoon of water for the egg wash. In the third shallow dish, combine the panko breadcrumbs and melted butter, mixing until the panko is evenly coated.
Step 5: Take each filled jalapeño half and dredge it first in the flour, shaking off any excess. Next, dip it into the egg wash, allowing any extra to drip off. Finally, thoroughly coat it in the panko-butter mixture, pressing gently to ensure the breadcrumbs adhere well.
Step 6: Arrange the breaded jalapeño poppers in a single layer on the prepared baking sheet, ensuring they are not touching.
Step 7: Bake for 20-25 minutes, or until the jalapeños are tender, the filling is bubbly, and the breading is golden brown and crispy. Keep an eye on them to prevent burning.
Step 8: Remove from the oven and let cool on the baking sheet for 5-10 minutes before serving. Serve warm with your favorite dipping sauce.