Soak the cashews for at least 4 hours up to overnight (8-12 hours). When ready, drain well. Preheat the oven to 400 F (200 F) degrees and line a baking sheet with parchment paper.
Slice each jalapeño in half lengthwise. Then, using a spoon remove the seeds and the white membrane inside the peppers. Be sure to wear gloves or wash your hands really well after handling the jalapeños.
Add the soaked cashews, lemon juice, nutritional yeast, garlic powder, water and salt to a high-speed blender and blend until completely smooth and thick creamy.
Transfer the cashew mixture to a bowl and add the cilantro and green onion. Mix to combine.
Add about 1/2 cup of panko crumbs to a shallow plate or bowl. If you run out of breadcrumbs, add more as needed. Stuff the jalapeño halves with cashew filling then press the filling into the breadcrumbs to coat. Place them on the baking sheet.
Bake for 20-25 minutes until the jalapeños are soft and the top is golden. If you like, you can broil them briefly at the end for some extra crunch on top.
Let cool for a few minutes before serving. Serve with a sprinkle of green onion, chives or parsley and buffalo sauce on the side, if desired.