Place the cornflour in a bowl and season with some salt and pepper.
Dip each piece of chicken into the seasoned flour and set aside.
Cook the potato slices in boiling salted water for about 5 minutes, then drain them in a colander or sieve and place to the side to cool. While the potatoes are cooking, follow the rest of the instructions below.
Add the garlic and seasoned chicken to the pan and cook until browned slightly.
Pour over the skimmed milk. Continue cooking until it thickens for about 2 minutes then season to taste.
Pour the contents of the pan into a casserole dish add the frozen peas and distribute evenly.
Top the chicken mixture with the potato slices and spray the top of the potatoes evenly using the cooking spray.
Bake in the centre of the oven for about 40 minutes until the potatoes are brown and crispy. I like to grill my potatoes for 5 minutes or so at the very end to get them crispier.
Notes
*I use Jersey Royal but you could also use Maris Peer or Charlotte.