In a medium-sized mixing bowl, combine the diced chicken with oil and seasoning until the chicken is fully coated.
In a large pan over medium-high heat, space out the chicken and fry both sides for 3-4 minutes until the chicken browns (should be cooked through at this point, but it will continue cooking later, so don't panic if it's not). Remove the chicken and place it in a bowl to one side, leaving any excess oil/fat in the pan.
Lower the heat to medium and add the pancetta. Fry until crispy with the fat rendered out, then add the onion and fry until soft and golden. There should be a good amount of fat in the pan now, but if it's very dry, you can add a dash of oil.
Stir the flour into the fat, then gradually pour in the stock, milk and then cream, whisking as you go to prevent lumps from forming. Stir in the parmesan until it melts, then stir in the chicken (plus any resting juices) and the sun dried tomatoes.
Bring to a simmer and stir now and then for 8-10mins until nice and thick, then check for seasoning and adjust if needed. Stir in the spinach until it wilts and combines, then pour into a baking dish and leave for 15 minutes or so until a 'skin' forms over the top. During this time, preheat the oven to 200C/400F.
Scatter over the diced focaccia, closing as many gaps as possible, then lightly spray with oil and bake for 18-20 minutes, or until golden and crisp on top and bubbly around the edges.
Serve and enjoy!