Place teff, stock, peas, and water into a heavy based saucepan on medium heat. Stirring occasionally until all the water is absorbed.
Add in onion and garlic, cook for 5 minutes. Remove from heat.
Add in parsley and cheeses and stir quickly for a couple of minutes until cheese is melted throughout.
Set aside and cool until at least lukewarm, and mixture can be easily handled.
Whisk egg and milk together in a bowl.
Roll teff mixture into balls a little bigger than golf balls.
Dunk into egg mixture and immediately roll into corn crumbs until the ball is covered.
Place onto a plate and repeat until all mixture is finished.
Place into the fridge for one hour until cold.
Heat oil in a fry pan and place arancini balls in a few at a time.
Turn balls carefully as they are cooking until they are completely golden brown.
Drain on paper towel and repeat until all balls are cooked.
Serve with napolitana sauce on top, extra Parmesan, and parsley.