Combine ground chicken, breadcrumbs, Parmesan cheese, parsley, onion, garlic, egg, Dijon mustard, salt, and pepper in a large mixing bowl. Mix well until everything is evenly combined.
Form the mixture into small patties, about 2-3 inches in diameter.
Using a large skillet, heat the olive oil over medium-high heat. Add the chicken patties and cook for 4-5 minutes on each side, until cooked through or golden brown.
Remove the chicken rissoles from the skillet and transfer them on a plate lined with a paper towel to absorb any excess oil.
Serve the chicken rissoles hot with your favorite dipping sauce or as a sandwich filling.