Place chickpeas in a large bowl. Cover with 2 inches of water and soak for 12 to 24 hours. Drain.
Place chickpeas, green onions, garlic, salt, cumin and chili powder in the bowl of food processor. Pulse until finely chopped. Add flour and baking powder; pulse to combine.
Squeeze a small amount of mixture. It should hold together and not be sticky. Add up to another 2 tablespoons (25g) flour if needed and pulse to combine. Transfer mixture to a medium bowl, cover and refrigerate for one hour or up to 24 hours.
Once chilled, use a small ice cream scoop or tablespoon to scoop balls. Flatten each to a generous 1/4-inch (1cm) thick patty and set aside on a rimmed baking sheet.
Heat oven to 250F (120C).
Add vegetable oil to a frying pan heat to 375F (190C). Fry patties in batches of 5 or 6 until golden brown, 4 to 6 minutes, flipping halfway. Transfer onto another rimmed baking sheet and place in oven to keep warm while frying remaining patties.
When ready to serve, whisk together hot sauce and butter in a large bowl until well combined. Remove patties from the oven and toss in sauce.