Preheat the oven to 350 degrees F and lightly grease a 9x13 inch casserole dish.
Soak the cashews: Bring 4 cups of water to a boil. Pour the hot water over the cashews and let soak for 5 minutes.
Make the cheese sauce: Drain the cashews and discard the soaking water. Add them to a blender along with 3 cups of fresh water, lemon juice, salt and tapioca starch. Blend until very smooth, and set aside. It will appear a bit watery, but that is right as it thickens while it bakes.
Cook the pasta: Cook the pasta according to package instructions, but one minute less. The noodles will continue to cook in the oven. Drain and set aside.
Sauté vegetables: In a small pan on the stove, sauté the onion, garlic and jalapeños in the olive oil for about 5 minutes, until softened. Remove from heat.
Add the drained, cooked pasta to the casserole dish. Pour the cheese sauce on top and add the vegetables. Stir to combine right in the dish.
In a small bowl, mix the panko breadcrumbs and melted vegan butter, then sprinkle the mixture on top of the pasta. Bake for 20 minutes until warm and bubbly, and the sauce has thickened. Do not over bake or the sauce will dry out. Enjoy!