Prep your station.
Preheat the oven to 400°F / 205°C and line two large baking sheets with parchment paper for easy cleanup.
Create the crust.
Cut the chicken breasts into 1-inch cubes and place them in a food processor.
Add the egg, salt, pepper, oregano, ground mustard, and onion powder. Process until the mixture forms a smooth, uniform paste.
Add the cheese.
Sprinkle in the grated Parmesan cheese and pulse just a few more times until it's fully incorporated. Be careful not to over-mix.
Form the flatbreads.
Divide the chicken mixture into four equal portions.
Place two mounds on each prepared baking sheet.
Using an offset spatula or the back of a wet spoon, spread each mound into a thin, tortilla-sized circle, about ¼-inch / 6 mm thick.
First bake.
Drizzle the flatbreads with olive oil and bake for 10 minutes, until the edges are golden and the crust is firm to the touch.
Add the toppings.
Remove the baking sheets from the oven.
Spread 2 teaspoons (10 ml / 0.3 fl oz) of pesto evenly over each crust.
Top with the shredded mozzarella, sliced goat cheese, and halved cherry tomatoes.
Finish with a generous grind of black pepper.
Final bake. Return the flatbreads to the oven and bake for another 15 minutes, or until the cheese is melted, bubbly, and beautifully golden brown.
Serve and enjoy.
Let the flatbreads cool for a minute or two on the pan before slicing into quarters and serving warm. Leftovers can be stored in the refrigerator for up to 3 days.
Don't have a food processor? You can use ground chicken instead. Simply mix all the crust thoroughly in a large bowl until well combined.
