Add the chickpeas to a mixing bowl and smash with a fork. Add the avocado, dijon, 1/2 of the pesto & 1/2 of the mayo and mix & mash until combined. Add the celery, red onion & dry seasonings and mix until combined. Taste and adjust the seasonings if needed. Cover and place in the fridge for 30 minutes - or until ready to assemble.
Cut the bread in half lengthwise and place on a baking sheet. Pick out some of the bread from the top half to make room for the filling. Spray with oil and toast in the oven under the broiler until browned.
Add the remaining pesto & mayo to a bowl and mix to combine.
To assemble, add the chickpea salad to the bottom half of the sandwich and top with the lettuce. To the top half, add the pesto mayo, sun-dried tomatoes & sprouts. Put the sandwich together, cut into 4-8 sandwiches and enjoy!
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Notes
Depending on how many people you are serving, this can easily be cut into 8 squares for smaller servings.
You can make the pesto from scratch or get it store-bought.
If you want to take the time to remove the skins from the chickpeas, go for it! I don't mind them so I leave them on.