For the sauce, mix mayonnaise and ketchup in a bowl. Then cover and set aside.
For the tempura batter, in a bowl, mix chickpea flour, all-purpose flour, nori, salt and water until smooth and thick. Cover and let rest in the refrigerator.
In the meantime, cut the mushroom stems into 5 mm thick rounds.
using a piping nozzle or an apple corer, remove the center of the rounds. (We will deep fry these parts as well).
Put oil in a saucepan and heat over high heat. When the oil is hot, dip the mushrooms in the batter and deep fry them for 2-3 minutes on both sides until golden.
Place the vegan calamari on a plate lined with paper towel, adjust salt and pepper and enjoy hot with the cocktail sauce.