Heat the vegan margarine in a large Dutch oven over medium heat. Add the diced onion and sauté for 3–4 minutes until softened. Stir in the garlic and cook for another 1 minute until fragrant.
Add the diced jalapeños, drained cashews, salt, garlic powder, onion powder, smoked paprika, nutritional yeast, miso paste, and flour. Stir to coat, then pour in the vegetable stock to deglaze the pot. Scrape any browned bits from the bottom.
Stir in the soy milk and bring to a gentle simmer. Reduce heat and cook for 5–7 minutes, stirring occasionally, until thickened. Remove from heat and transfer the mixture to a high-speed blender. Blend until smooth and creamy.
Return the sauce to the Dutch oven and stir in the cooked macaroni until evenly coated.
Spoon the mac n cheese mixture into silicone ice cube trays or lightly greased standard ice cube trays. Press down to compact. Freeze for at least 4 hours, or until solid.
Once frozen, prepare the breading. Set out three shallow bowls: one with flour and salt, one with the aquafaba, and one with the panko breadcrumbs.
Pop the frozen mac n cheese cubes out of the trays. Working one at a time, dip each cube into aquafaba, then into flour, then back into aquafaba, and finally coat in panko crumbs. Repeat until all are breaded.
Heat 2–3 inches of vegetable oil in a deep pot or Dutch oven to 340°F (170°C). Carefully lower a few bites into the oil at a time (don’t overcrowd). Fry for 3–4 minutes or until golden brown and crispy.
Use a slotted spoon to transfer to a paper towel-lined plate. Sprinkle with salt and serve hot with your favorite dipping sauce like tomato relish, sweet chili, or vegan aioli.