20 Minute Free Form Chicken Pot Pie (from scratch, no cream)

Ingredients:

1 sheet puff pastry (25cm x 25cm / 10" x 10"), thawed
Oil spray
2 tbsp butter
400g/13oz chicken thigh fillets (or tenderloin or breast), cut into small bite size pieces
1 onion (small, brown, white or yellow), diced
2 garlic cloves, minced
2 bacon rashers, diced
¼ cup marsala (or dry sherry, port or white wine) (see notes)
2 tbsp plain flour
2 cups frozen mixed peas, corn and carrots, thawed
2 cups small broccoli florets (see notes)
2 cups milk (full cream or low fat)
½ cup grated cheese
¼ tsp salt (plus more to taste)
Black pepper

Directions: