Drain, rinse, and dry the canned chickpeas. Then, in a skillet over medium heat, lightly toast them for 3 minutes in the olive oil, seasoning with thyme and sea salt, until they begin to turn tender and creamy.
Transfer the chickpeas to a food processor and add the roughly chopped pistachios (as well as the dried sheet of seaweed, if you wish). Pulse a couple times, until there are no whole chickpeas left (photos for reference below).
Transfer the chickpea mixture to a medium bowl, and add to it the mayo, lemon juice, nutritional yeast, Worchestire sauce, yellow onion, and pickles. Mix well until everything is incorporated.
Set your oven to broil. On a baking sheet, halve your english muffins into 4 single muffin halves. Butter them and garnish with a tiny bit of garlic powder. Broil the muffins for a couple minutes, until they begin to turn a light golden brown. Watch them carefully.
Take out your muffins, and load them high with chickpea tuna melt batter. Return it to the broiler for another another couple minutes, until the tops begin to brown.
Remove the chickpea tuna melts from the oven one last time, and top each with a half slice of vegan cheese. Return to the broiler to let the cheese melt, about a minute or two.