Heat oven to 375 degrees. Place the panko on a rimmed baking sheet, spray with cooking spray and bake until toasted and golden-brown, about 5-7 minutes. Season mixture with salt and pepper, transfer to a bowl and set aside to cool. Line the baking sheet with parchment paper.

Place the oats in a food processor fitted with the blade attachment and pulse into a fine flour. Transfer to a large bowl.

Drain the chickpeas into a mesh sieve set over a bowl to catch the liquid. Place the chickpeas into the food processor and add the salt, garlic powder, onion powder, mustard powder and paprika. Pulse until mixture is crumbly. Whisk 1/4 cup of the chickpea liquid in a small mixing bowl until foamy. Add liquid and oat flour to food processor and pulse until the mixture forms a ball.

Divide the chickpea mixture into equal portions and shape each one into a small patty about the same size as a slider bun. Spray both sides of each patty in cooking spray and coat in the toasted panko.

Place on the parchment-lined baking sheet and bake until crispy, about 20 minutes.

Measure out 1/4 cup of the bean liquid (aquafaba) in a large glass measuring cup. Add vinegar, salt, sugar, lemon juice and dry mustard. Using an immersion blender, mix until combined. With the blender running, very slowly drizzle in the oil in a thin stream. Miix until thickened and the consistency of mayonnaise.