In a large bowl, add the chickpeas, and using the back of a fork, mash the chickpeas into a crumbly texture
Add all the other ingredients and mix thoroughly
Spread a generous amount of butter on both sides of the bread slices
On one side of one slice, cover the surface of the bread with the chickpeas mixture, then gently add the other slice to cover
Place the flat pan over low to medium fire
Gently place the sandwich on the heated pan, and using a flat utensil, press the sandwich down, cooking the buttered side of the bread
Check if the bottom side is golden brown, then flip and repeat with the top side of the sandwich (continually press the sandwich down to melt and cook the inside of the sandwich)
Once both sides are golden brown, take the sandwich off heat
Using a sharp bread knife, cut the sandwich in half on a clean chopping board and serve with a drizzle of extra pesto at the opening of the sandwich.