Preheat oven to 350 °F. Lightly grease or line a cookie sheet with parchment paper and set aside. Alternatively, you can use an Air Fryer, set at 200 degrees for 12 minutes.
In a medium bowl, mash chickpeas with a fork or potato masher until coarse. You don't want any whole beans left, but don't overly mash them so that they are pureed and resembling refried beans. Add in oats, mayonnaise, mustard, spices and cornstarch. Mix well. If the mixture is too wet, add some of the breadcrumbs. Correct seasoning if needed.
Pour breadcrumbs into a shallow plate.
Pour the chickpeas liquid into another shallow plate.
Using a spoon, portion your nuggets and flatten in the palm of your hand to it resembles a nugget shape.
Dip into the chickpea liquid mixture so that it's coated on both side then press into breadcrumbs on each side, making sure it's completely coated. Place nugget on a cookie sheet and repeat with all nuggets. Bake nuggets for 10 minutes, flip and bake another 10-15 minutes, until nuggets are firm, golden and crispy.